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.