light blue in model B); and one with a diamond-shaped keystone (the Gothic arch, model C). Flying buttresses act the same way ancient Roman columns did, countering the horizontal force of the arch.

These aboveground arches were, in fact, only a small section of an aqueduct system. Roman engineers would create a gentle downward slope all the way from start to finish, since the only force ...

Photos show the eerie ruins. A view into the ancient Roman aqueduct. Photo from A. Belleli and Inrap The ancient Romans built ...