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 …