Very few of us have ever set foot near a gen­uine medieval cas­tle, espe­cial­ly if we don’t hap­pen to live in Europe. Yet prac­ti­cal­ly all of us still, here in the twen­ty-first cen­tu­ry, refer with some fre­quen­cy to their com­po­nents in our every­day speech. When we invoke moats, draw­bridges, dun­geons, and even cat­a­pults, we almost always do so metaphor­i­cal­ly — assum­ing we’re not active mem­bers of a his­tor­i­cal re-cre­ation soci­ety — yet we also have no prob­lem see­ing them before our mind’s eye with what feels like per­fect clar­i­ty. The dif­fi­cul­ty comes if we attempt to inte­grate all of those images, absorbed hap­haz­ard­ly from folk tales and pop­u­lar cul­ture, into a func­tion­ing whole.

The fact of the mat­ter is that peo­ple in the Mid­dle Ages real­ly did live and work in cas­tles, and occa­sion­al­ly had to defend them, or indeed attack them. Using a 3D-ren­dered repli­ca con­struct­ed to reflect how those struc­tures were built in the frag­ment­ed Europe of the eleventh through four­teenth cen­turies after the fall of the Car­olin­gian Empire, the Decon­struct­ed video above explains every­thing about how they worked in the span of about twen­ty min­utes.

This tour begins with the bar­bi­can: not the cel­e­brat­ed Bru­tal­ist com­plex in Lon­don, but the exte­ri­or for­ti­fied pas­sage “designed to expose attack­ers to defen­sive fire before they even reach the main gate.” And it only gets hard­er for would-be cas­tle cap­tors from there.

Para­pets with cutouts through which archers could fire their arrows, the moat that made under­min­ing (a term com­mon enough in mod­ern lan­guage that few now rec­og­nize its ori­gins) next to impos­si­ble, the draw­bridge that could be pulled up, the walls slant­ed to repel bat­ter­ing rams, the spiked portcullis­es that could be slammed down: these are just a few of the myr­i­ad defens­es that made invaders’ lives dif­fi­cult — and, in many cas­es, short, espe­cial­ly when “mur­der holes” were involved. (Now there’s a term just wait­ing for inclu­sion in our lex­i­con.) The exam­ple con­struct­ed here rep­re­sents the zenith of cas­tle design, the cul­mi­na­tion of an evo­lu­tion­ary process that began in the tenth cen­tu­ry with a struc­ture called the motte and bai­ley: a term that, if you don’t already know it from oth­er con­texts, you prob­a­bly just don’t do enough ver­bal bat­tle on the inter­net.

Relat­ed Con­tent:

How To Build a 13th-Cen­tu­ry Cas­tle, Using Only Authen­tic Medieval Tools & Tech­niques

Behold a 21st-Cen­tu­ry Medieval Cas­tle Being Built with Only Tools & Mate­ri­als from the Mid­dle Ages

The Tech­nol­o­gy That Brought Down Medieval Cas­tles and Changed the Mid­dle Ages

How Medieval Cathe­drals Were Built With­out Sci­ence, or Even Math­e­mat­ics

The Roman Colos­se­um Decon­struct­ed: 3D Ani­ma­tion Reveals the Hid­den Tech­nol­o­gy That Pow­ered Rome’s Great Are­na

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.

The arti­fi­cial lan­guage of Esperan­to was con­ceived with high ideals in mind. In the eigh­teen-eight­ies, its cre­ator L. L. Zamen­hof envi­sioned it as the uni­ver­sal sec­ond lan­guage of human­i­ty, and if it has­n’t achieved that sta­tus by now, it at least remains the world’s most wide­ly spo­ken con­struct­ed aux­il­iary lan­guage. One fac­tor com­pli­cat­ing its spread is that no lan­guage, even one guid­ed by inter­na­tion­al­ism, can remain the same for long enough in two dif­fer­ent cul­tures. As in spo­ken and writ­ten lan­guages, so in the con­crete one of archi­tec­ture — and in the case of the style known as Bru­tal­ism, that would be lit­er­al con­crete. Meant to make human­i­ty whole again after the Sec­ond World War, its build­ings end­ed up being rather more par­tic­u­lar, and less utopi­an, than their archi­tects intend­ed.

Exam­ples aplen­ty appear in the new video above from Built Nar­ra­tive, which offers what amounts to a post­card tour of Bru­tal­ist (and Bru­tal­ism-adja­cent) build­ings from around the world. Named for its main mate­r­i­al béton brut, or raw con­crete, the style came into its own dur­ing the rebuild­ing of war-ruined sec­tions of British and con­ti­nen­tal Euro­pean cities — and, over in the U.S., the rapid pro­lif­er­a­tion and expan­sion of col­lege cam­pus­es — which had to be done quick­ly and under less-than-extrav­a­gant bud­gets.

Libraries, research facil­i­ties, city halls, admin­is­tra­tive build­ings, cour­t­hous­es, hous­ing projects: these are the sorts of struc­tures that most often took Bru­tal­ist form in the nine­teen-fifties, six­ties, and sev­en­ties, result­ing in the insti­tu­tion­al, bureau­crat­ic, and in some places total­i­tar­i­an asso­ci­a­tions it still has today.

Some pub­licly loathed Bru­tal­ist build­ings, like the Tri­corn Cen­tre in Portsmouth and the Third Church of Christ, Sci­en­tist in Wash­ing­ton, D.C. have been torn down, often after decades of neg­li­gent main­te­nance. Oth­ers, like the Bar­bi­can Estate in Lon­don or Habi­tat 67 in Mon­tre­al, are now beloved sites of pil­grim­age. Wide­ly acknowl­edged mas­ters of Bru­tal­ism include Le Cor­busier, who pio­neered it with build­ings like the Unité d’Habi­ta­tion in Mar­seille (not Berlin, con­tra the cap­tion in the video) and Ken­zo Tange (pro­nounced “tawn-gay,” not “tang” as the nar­ra­tor says it), whose work steered the Japan­ese ver­sion of the move­ment in its own sub­tle, some­times play­ful direc­tions. Now, thanks in part to the rapid dif­fu­sion of archi­tec­tur­al pho­tog­ra­phy made pos­si­ble by social media, a new enthu­si­ast of Bru­tal­ism seems to be born every minute. Even if they don’t believe that archi­tec­ture can bring a new world into being, they still feel the pull of a future that nev­er came — or, at any rate, has­n’t come yet.

Relat­ed Con­tent:

Every­thing You Ever Want­ed to Know About the Beau­ty of Bru­tal­ist Archi­tec­ture: An Intro­duc­tion in Six Videos

Why Peo­ple Hate Bru­tal­ist Build­ings on Amer­i­can Col­lege Cam­pus­es

Why Do Peo­ple Hate Mod­ern Archi­tec­ture?: A Video Essay

Good­bye to the Nak­a­gin Cap­sule Tow­er, Tokyo’s Strangest and Most Utopi­an Apart­ment Build­ing

The World Accord­ing to Le Cor­busier: An Ani­mat­ed Intro­duc­tion to the Most Mod­ern of All Archi­tects

An Espres­so Mak­er Made in Le Corbusier’s Bru­tal­ist Archi­tec­tur­al Style: Raw Con­crete on the Out­side, High-End Parts on the Inside

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.

Sci­ence and engi­neer­ing may be con­flat­ed to some degree in the pub­lic mind, but any­one who’s spent much time in an aca­d­e­m­ic depart­ment belong­ing to one or the oth­er of those branch­es of endeav­or knows how insis­tent­ly dis­tinc­tions can be drawn between them. Bill Ham­mack, a pro­fes­sor of engi­neer­ing at the Uni­ver­si­ty of Illi­nois Urbana-Cham­paign who’s been there since he was a mas­ter’s stu­dent in 1986, sure­ly has his own thoughts on the sub­ject. The video above from his pop­u­lar YouTube chan­nel Engi­neer­guy explains how cathe­drals were designed in the Mid­dle Ages, using the exam­ple of Sainte-Chapelle in Paris. Specif­i­cal­ly, it gets into how such a build­ing’s arch­es and sup­port­ing walls could have been engi­neered with­out the aid of sci­ence at all, or even the use of math­e­mat­ics.

Com­pared to today, the scope of knowl­edge human­i­ty com­mand­ed back in medieval times may have been impos­si­bly nar­row — to say noth­ing of the knowl­edge pos­sessed by any giv­en human, espe­cial­ly out­side the lit­er­ate elite. Yet what was then known proved more than suf­fi­cient to build struc­tures that still stand, and indeed impress, many cen­turies (and in some cas­es, more than a mil­len­ni­um) lat­er.

Ham­mack explains that, in the place of mak­ing cal­cu­la­tions, their builders would per­form actions. For instance, a medieval mason would have made a life-size chalk draw­ing of the arch, laid a rope along its form, and cut the rope’s length to match that of the arch. He could then use the rope to deter­mine just how thick the wall would need to be, between a fourth and a fifth of the arch’s span, with­out a num­ber ever being involved.

Ham­mack notes that the Romans, too, under­stood this nec­es­sary pro­por­tion for arch con­struc­tion. “The pro­por­tion­al rule does­n’t come from some sci­en­tif­ic analy­sis of stone and its prop­er­ties,” he says. “It comes from cen­turies of expe­ri­ence, from tri­al and error.” Such heuris­tics, or rules of thumb, con­sti­tute “an impre­cise method used as a short­cut to find a solu­tion to a prob­lem, often by nar­row­ing the range of pos­si­ble solu­tions.” They’re also employed in the engi­neer­ing method to “cause the best change in a poor­ly under­stood sit­u­a­tion using avail­able resources.” Its thor­ough­go­ing prac­ti­cal­i­ty would seem to have lit­tle to do with the dif­fer­ent sort of rig­ors that apply in sci­ence, where estab­lish­ing truth, or at least the absence of false­ness, is all. Belief in the engi­neer­ing approach to prob­lems like this does­n’t require faith in the reli­gious sense, but if you like, you can find proof of its effec­tive­ness in hous­es of wor­ship from Sainte-Chapelle to the Pan­theon to Hagia Sophia — or at least in their arch­es.

Relat­ed Con­tent:

Göbek­li Tepe: The 12,000-Year-Old Ruins That Rewrite the Sto­ry of Civ­i­liza­tion

The Cre­ation & Restora­tion of Notre-Dame Cathe­dral, Ani­mat­ed

An Ani­mat­ed Video Shows the Build­ing of a Medieval Bridge: 45 Years of Con­struc­tion in 3 Min­utes

Behold a 21st-Cen­tu­ry Medieval Cas­tle Being Built with Only Tools & Mate­ri­als from the Mid­dle Ages

How Design­ing Build­ings Upside-Down Rev­o­lu­tion­ized Archi­tec­ture, Mak­ing Pos­si­ble St. Paul’s Cathe­dral, Sagra­da Família & More

The Longest Con­struc­tion Projects in His­to­ry: Why Sagra­da Família, the Milan Duo­mo, Greek Tem­ples & Oth­er Famous Struc­tures Took Gen­er­a­tions to Com­plete

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.

We’ve all stayed at the Chelsea Hotel, though most of us have done so only in our minds, through such cul­tur­al arti­facts as Leonard Cohen’s “Chelsea Hotel No. 2,” Bob Dylan’s “Sara,” Nico’s “Chelsea Girls,” Andy Warhol’s epony­mous film that includes the Nico song, or Pat­ti Smith’s Just Kids, which tells of the time she spent there with Robert Map­plethor­pe. Enthu­si­asts of the work of every­one from Janis Joplin to Arthur C. Clarke to Miloš For­man to Dylan Thomas to Mark Twain may not know that they, too, there­by enjoy an indi­rect con­nec­tion to that New York insti­tu­tion, which has stood on West 23rd Street since its con­struc­tion in 1884.

At that time, it also stood quite tall, loom­ing over every oth­er apart­ment build­ing in the city, and indeed over most of the rest of Man­hat­tan. Nowa­days, how­ev­er, the cul­tur­al pro­file of the Chelsea Hotel (offi­cial­ly, and less cool­ly, the Hotel Chelsea) is high­er than its phys­i­cal one ever was.

Its rep­u­ta­tion as a refuge for artists dates to the man­age­ment of Stan­ley Bard, who inher­it­ed the busi­ness from his father in 1964. Already, a degree of dilap­i­da­tion in the build­ing itself, as well as the sur­round­ing neigh­bor­hood, kept rents low enough to attract impe­cu­nious cre­ative types. Bard dis­played enough gen­eros­i­ty to artists that, before long, Andy Warhol’s fac­to­ry had more or less moved in.

The Chelsea’s lat­est trans­for­ma­tion began in the mid-two-thou­sands with a series of takeovers and ren­o­va­tions not nec­es­sar­i­ly wel­comed by the exist­ing long-term res­i­dents, who appre­ci­at­ed the hotel pre­cise­ly for its seem­ing imper­vi­ous­ness to gen­tri­fi­ca­tion. In the new Archi­tec­tur­al Digest video above, cur­rent own­er Sean MacPher­son gives a tour of the lux­u­ri­ous Chelsea of the twen­ty-twen­ties, all of whose spaces have been metic­u­lous­ly curat­ed to evoke its sto­ried past. In its bar (with cig­a­rette burns care­ful­ly pre­served) guests can order a cock­tail called the Two Dylans, named in homage to both Bob and Thomas; in the base­ment, they can choose from the largest selec­tion of Japan­ese whiskey at a new restau­rant named after for­mer res­i­dent Teruko Yokoi. The expe­ri­ence of a nine­teen-six­ties New York bohemi­an is now avail­able to all of us — or at least those of us who can come up with $500 per night.

If you want to revis­it the hotel dur­ing its pre-restora­tion hey­day, you can watch the 1981 doc­u­men­tary below. It will let you get glimpses of Andy Warhol, William S. Bur­roughs, Nico, and more.

Relat­ed con­tent:

New York’s Famous Chelsea Hotel and Its Cre­ative Res­i­dents Revis­it­ed in a 1981 Doc­u­men­tary

Vin­tage Footage Shows a Young, Unknown Pat­ti Smith & Robert Map­plethor­pe Liv­ing at the Famed Chelsea Hotel (1970)

Nico Sings “Chelsea Girls” in the Famous Chelsea Hotel

Thanks­giv­ing Menu at the Plaza Hotel in New York City (1899)

Watch Iggy Pop Per­form Dylan Thomas’ “Do Not Go Gen­tle Into That Good Night”

Archi­tect Breaks Down Five of the Most Icon­ic New York City Apart­ments

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.

Apart from a few bridges that still work, the infra­struc­tur­al achieve­ments of the Roman Empire exist, for us, most­ly as ruins. With a lit­tle imag­i­na­tion, those his­toric sites give us a clear enough sense of the empire’s sheer might, but if we want to go deep­er, we should then look into the numer­ous Roman con­struc­tions that haven’t sur­vived at all. In the video below from his chan­nel Told in Stone, ancient-his­to­ry YouTu­ber Gar­rett Ryan gives his per­son­al top sev­en “lost Roman won­ders,” begin­ning with Trajan’s Bridge, whose length of more than a kilo­me­ter across the Danube made it the longest bridge ever built at that time: a project of ambi­tions befit­ting a man that his­to­ry remem­bers as one of the “Five Good Emper­ors.”

No such sta­tus for Nero, though he did com­mis­sion the Subi­a­co Dams. Nec­es­sary to cre­ate a series of arti­fi­cial lakes beneath the infa­mous ruler’s vil­la, they were the high­est dams in exis­tence until the Mid­dle Ages. Hadri­an’s more pub­lic-mind­ed white-mar­ble tem­ple at Cyz­i­cus in mod­ern-day Turkey was known as unusu­al­ly splen­did even by the stan­dards of that genre of build­ing; now only its foun­da­tions remain, with archae­o­log­i­cal digs turn­ing up the occa­sion­al frag­ment.

In the for­mer Con­stan­tino­ple, the Church of the Holy Apos­tles is remem­bered as the sec­ond-most famous van­ished ear­ly Chris­t­ian church, after only the old St. Peter’s Basil­i­ca in Rome. Hagia Sophia may still be around, but the Col­umn of Jus­tin­ian that once stood between it and the Great Palace was melt­ed down for scrap long ago.

We only know of these lost struc­tures because we have his­tor­i­cal attes­ta­tions of their exis­tence, most vivid­ly in paint­ings: take the Pyra­mid of Romu­lus, a strik­ing tomb that appears near the Vat­i­can in The Vision of the Cross, which Raphael’s assis­tants pro­duced after his death. Oth­ers, like the Colos­sus of Nero from which the Colos­se­um takes its name, are rep­re­sent­ed on coins. In the video at the top, Ryan cov­ers three more “for­got­ten Roman megapro­jects”: Claudius’ tun­nel of record-mak­ing length through the moun­tain between the Riv­er Liris and the Fucine Lake, Tra­jan’s mil­i­tary high­way through the “Iron Gates” of the Danube, and Octa­vian’s secret har­bor at Lake Aver­nus. In our time, of course, there are no more emper­ors, Roman or oth­er­wise, and we’re sure­ly bet­ter off for it. But we can still admire — to use a twen­ty-first cen­tu­ry con­cept — the state capac­i­ty they com­mand­ed.

Relat­ed con­tent:

The Advanced Tech­nol­o­gy of Ancient Rome: Auto­mat­ic Doors, Water Clocks, Vend­ing Machines & More

How the Ancient Romans Built Their Roads, the Life­lines of Their Vast Empire

The Genius Engi­neer­ing of Roman Aque­ducts

The Roman Colos­se­um Decon­struct­ed: 3D Ani­ma­tion Reveals the Hid­den Tech­nol­o­gy That Pow­ered Rome’s Great Are­na

The Amaz­ing Engi­neer­ing of Roman Baths

Built to Last: How Ancient Roman Bridges Can Still With­stand the Weight of Mod­ern Cars & Trucks

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.

The play­wright Tris­tan Bernard is said to have eat­en lunch at the Eif­fel Tow­er every day, but not because he liked the menu in its café: rather, because it was the only place in Paris with no view of the Eif­fel Tow­er. His view wasn’t whol­ly eccen­tric in the decades after its con­struc­tion, in the late eigh­teen-eight­ies, when the struc­ture had yet to become the most beloved in France, and per­haps in the world. Yet not far behind the Eif­fel Tow­er as a must-vis­it tourist attrac­tion in a town full of them is Paris’ least beloved build­ing: the Tour Mont­par­nasse, which since its com­ple­tion in 1973 has stood in infamy as the only sky­scraper in the cen­ter of the city.

Unlike the Eif­fel Tow­er, which was com­mis­sioned in part to cel­e­brate the cen­ten­ni­al of the French Rev­o­lu­tion, the Tour Mont­par­nasse projects no polit­i­cal sym­bol­ism; unlike Notre-Dame de Paris, or Sacré-Cœur de Mont­martre, it has no reli­gious sig­nif­i­cance. Its pur­pose is whol­ly com­mer­cial, befit­ting a large office build­ing with a shop­ping mall — or now, the remains of a shop­ping mall — at the bot­tom. But when it was first con­ceived in 1958, it embod­ied the very image of moder­ni­ty in a built envi­ron­ment that was dilap­i­dat­ed where it wasn’t war-torn. A mod­ern sky­scraper would show the world, unmis­tak­ably, that Paris had stepped ful­ly into the twen­ti­eth cen­tu­ry of indoor plumb­ing, elec­tric­i­ty, fast trains, and telecom­mu­ni­ca­tion.

This mis­sion gained the full back­ing of none oth­er than Andre Mal­raux, then France’s first Min­is­ter of Cul­tur­al Affairs. Unfor­tu­nate­ly, nine­teen-fifties Europe lacked the tech­nol­o­gy, exper­tise, and mon­ey required for a 60-sto­ry sky­scraper, let alone one serv­ing as the cen­ter­piece of a sweep­ing rede­vel­op­ment project that includ­ed gleam­ing new res­i­den­tial blocks and a com­plete­ly rebuilt Mont­par­nasse Sta­tion. The tow­er could­n’t even break ground until 1969, by which time the build­ing’s once-cut­ting-edge mid-cen­tu­ry design — hard­ly a uni­ver­sal hit even in maque­tte form — had already begun to look passé. (Part of the prob­lem was sure­ly its col­or, which archi­tect Philippe Tré­ti­ack described as hav­ing “a touch of the nico­tine stain about it.”)

When the Tour Mont­par­nasse turned 50 a few years ago, I hap­pened to be in Paris on my hon­ey­moon. Noth­ing was hap­pen­ing to mark the occa­sion, apart from the long-ongo­ing dis­cus­sions about whether to ren­o­vate the thing or just knock it down. The for­mer option hav­ing won the day, you can see the details of the planned extreme makeover in the B1M video above. Rather than destroy­ing the exist­ing build­ing, the idea is to do the next best thing and make it invis­i­ble. This ambi­tious project will install a new façade of clear glass and bands of sky gar­dens, among oth­er changes, in order to light­en its bur­den­some visu­al mass. But how­ev­er rad­i­cal its trans­for­ma­tion, one sus­pects that it will remain most appre­ci­at­ed as the only place in Paris with­out a view of the Tour Mont­par­nasse.

Relat­ed con­tent:

How Paris Became Paris: The Sto­ry Behind Its Icon­ic Squares, Bridges, Mon­u­ments & Boule­vards

Watch the Build­ing of the Eif­fel Tow­er in Time­lapse Ani­ma­tion

The Archi­tec­tur­al His­to­ry of the Lou­vre: 800 Years in Three Min­utes

The Cre­ation & Restora­tion of Notre-Dame Cathe­dral, Ani­mat­ed

Why Europe Has So Few Sky­scrap­ers

Why Do Peo­ple Hate Mod­ern Archi­tec­ture?: A Video Essay

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.

No one who trav­els to Flo­rence can help see­ing the dome of the Cathe­dral of Saint Mary of the Flower. That’s true not just because of its sheer loom­ing phys­i­cal pres­ence over the rest of the city, but also because of its impor­tance as an achieve­ment in var­i­ous kinds of his­to­ry, from that of engi­neer­ing to archi­tec­ture to reli­gion. Its sto­ry is told by art his­to­ri­ans Beth Har­ris and Steven Zuck­er in their new Smarthis­to­ry video above, which begins in the year 1417. At the time, Zuck­er explains, Flo­rence had a “huge” prob­lem: the ground­work for its ambi­tious­ly large cathe­dral had been laid a cen­tu­ry before, but nobody knew how to build the dome for which its plans called.

The assump­tion, says Har­ris, was that “by the time they had to build it, they would fig­ure out how to do it,” a reflec­tion of both the more relaxed speed of con­struc­tion in the fif­teenth cen­tu­ry, as well as a pace of inno­va­tion that must have felt rapid­ly on the increase.

Such a struc­ture had­n’t been built since the Pan­theon in antiq­ui­ty, the out­do­ing of which would, at least in the­o­ry, con­firm Florence’s recep­tion of the torch of civ­i­liza­tion from Rome. But none of the tra­di­tion­al tech­niques could sup­port a dome of this size, atop so high a tow­er, dur­ing con­struc­tion. Sal­va­tion even­tu­al­ly came in the unpromis­ing form of Fil­ip­po Brunelleschi, an archi­tect, sculp­tor, and gold­smith with­out much of a résumé — but, cru­cial­ly, with a deep under­stand­ing of the Pan­theon.

“Brunelleschi real­ized that hemi­spher­i­cal domes func­tion in a self-sup­port­ing man­ner if they’re con­struct­ed out of self-sup­port­ing con­cen­tric cir­cles,” Zuck­er says, and his chal­lenge was to use that knowl­edge to build an octag­o­nal dome. This involved design­ing two domes, a thick inner one cov­ered by a thin out­er one. Drop €30 on a tick­et, and you can ascend the stairs through the inter-dome gap your­self. There the walls reveal the her­ring­bone brick pat­tern that kept the struc­ture sta­ble; at a larg­er scale, those bricks form struc­tur­al ele­ments, much like over­sized ver­sions of the stones used to build arch­es since time immemo­r­i­al. Regard­ing almost any pic­ture of Flo­rence, your eye may go straight to the cathe­dral, drawn both to the dome and to the splen­dor of its oth­er era-mix­ing archi­tec­tur­al fea­tures. But only from the inside can you under­stand how it all works.

Relat­ed con­tent:

How the World’s Biggest Dome Was Built: The Sto­ry of Fil­ip­po Brunelleschi and the Duo­mo in Flo­rence

How Fil­ip­po Brunelleschi, Untrained in Archi­tec­ture or Engi­neer­ing, Built the World’s Largest Dome at the Dawn of the Renais­sance

The Beau­ty & Inge­nu­ity of the Pan­theon, Ancient Rome’s Best-Pre­served Mon­u­ment: An Intro­duc­tion

Why Hasn’t the Pantheon’s Dome Col­lapsed?: How the Romans Engi­neered the Dome to Last 19 Cen­turies and Count­ing

How Design­ing Build­ings Upside-Down Rev­o­lu­tion­ized Archi­tec­ture, Mak­ing Pos­si­ble St. Paul’s Cathe­dral, Sagra­da Família & More

His­to­ri­an Answers Burn­ing Ques­tions About The Renais­sance

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.

We know more or less every­thing we could pos­si­bly know about ancient Egypt­ian civ­i­liza­tion. That owes in large part to the advanced state of record-keep­ing it achieved, and how many of its writ­ings have sur­vived, up to and includ­ing — as pre­vi­ous­ly fea­tured here on Open Cul­ture — a home­work assign­ment and a list of excus­es giv­en by builders who missed work. There just hap­pens to be one espe­cial­ly glar­ing gap in our knowl­edge: exact­ly how the ancient Egyp­tians built the Pyra­mids of Giza. This inter­sec­tion of rel­a­tive igno­rance and extreme fas­ci­na­tion has, as archi­tec­ture YouTu­ber Dami Lee acknowl­edges in the video above, inspired no end of crack­pot-ism. Noth­ing could be as unpromis­ing as unso­licit­ed con­tact from some­one claim­ing to have dis­cov­ered the secret of the pyra­mids.

The case of a Kore­an inde­pen­dent researcher called Huni Choi proved to be dif­fer­ent, for rea­sons Lee uses the video to lay out. Con­ven­tion­al assump­tions about how the pyra­mids were built hold that work­ers would have had to drag the stones up one or more ramps, though the dimen­sions of the struc­tures dic­tate that the project would neces­si­tate huge, com­plex, or huge and com­plex ramp sys­tems — whose own con­struc­tion has some­how left behind not a trace of evi­dence.

Accord­ing to Choi, “the Great Pyra­mid was­n’t built on its own, but through a chain of ‘sac­ri­fi­cial’ struc­tures” designed to be “can­ni­bal­ized.” The idea is that the pyra­mids were “over­built,” start­ing with a gigan­tic “trape­zoidal mass” with an inte­grat­ed ramp sys­tem, which, after being topped out, was then carved down into the pyra­mid shape we still find so famil­iar and com­pelling.

If true, Choi’s the­o­ry would solve the long-intractable prob­lem of the point­ed tops, which posed such a thorny engi­neer­ing prob­lem that even oth­er pyra­mid-build­ing civ­i­liza­tions seem­ing­ly avoid­ed even attempt­ing them. It also accounts for how the Egypt­ian design­ers and builders could have kept an eye on the angles all the while, in order to make sure the things were going up straight. And what of the left­over stone cut away from each pyra­mid? Why, it would sim­ply have been re-used for the con­struc­tion of the next one. This all squares not just with the esti­mat­ed mass of the Giza com­plex, but also with appar­ent ancient Egypt­ian atti­tudes toward the nat­ur­al and built envi­ron­ment. Alas, unlike in, say, physics, an archae­o­log­i­cal the­o­ry like this one remains dif­fi­cult to prove dis­pos­i­tive­ly, bar­ring anoth­er tech­no­log­i­cal break­through that enables a new form of analy­sis of the pyra­mids them­selves. Still, it’s a lot more sat­is­fy­ing than just assum­ing some ancient aliens did it.

Relat­ed con­tent:

Pyra­mids of Giza: Ancient Egypt­ian Art and Archaeology–a Free Online Course from Har­vard

A Walk­ing Tour Around the Pyra­mids of Giza: 2 Hours in Hi Def

Who Real­ly Built the Egypt­ian Pyra­mids — and How Did They Do It?

How Did They Build the Great Pyra­mid of Giza?: An Ani­mat­ed Intro­duc­tion

Ancient Egypt­ian Pyra­mids May Have Been Built with Water: A New Study Explore the Use of Hydraulic Lifts

Isaac New­ton The­o­rized That the Egypt­ian Pyra­mids Revealed the Tim­ing of the Apoc­a­lypse: See His Burnt Man­u­script from the 1680s

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.