Baptisterium
Encyclopedia
Classical antiquity
Classical antiquity is a broad term for a long period of cultural history centered on the Mediterranean Sea, comprising the interlocking civilizations of ancient Greece and ancient Rome, collectively known as the Greco-Roman world...
, a baptisterium was a large basin installed in private or public baths
Thermae
In ancient Rome, thermae and balnea were facilities for bathing...
into which bathers could plunge, or even swim about. It is more commonly called natatorium or piscina.