Many of ancient Rome's engineering innovations originated in one of its most important institutions: the bath.

Many of ancient Rome's engineering innovations originated in one of its most important institutions: the bath. A vital locus of leisure and social interaction, the public bathhouse incorporated intricate systems for plumbing and heating, sophisticated vaulted ceilings and a revolutionary new building material now known as concrete. Just what recipe of sand, lime, water and rubble did the Roman builders use to make their watertight concrete? How did they design and cast the domes and vaults that resulted in such graceful, airy interior spaces? And how did they create the ingenious plumbing and heating that accounted for the baths' vaunted comfort? In Sardis, Turkey, NOVA sets out to recreate an authentic working Roman bath, complete with hot tubs, cold plunges and underfloor heating.