What is known as the swimming pool in a Roman bathing establishment?

The term that refers to the swimming pool in a Roman bathing establishment is "Natatio." In ancient Roman baths, the natatio was typically a large open area that contained a pool for swimming and socializing, reflecting the Roman emphasis on leisure and communal activities. This space was often designed for relaxation and enjoyment after engaging in various bath rituals.

In contrast, other options represent different features of a Roman bath complex. "Piscina," while it does mean 'pool,' typically refers more generally to any pool or pond rather than specifically the swimming pool found in bathing establishments. "Laconicum" refers to a type of hot room that was used for sweating, similar to a sauna, and "Nymphaeum" describes a decorative structure dedicated to the nymphs, often featuring water fountains, but not serving as a swimming pool itself.