In Roman baths, the hot bath chamber is known as?

In Roman baths, the hot bath chamber is referred to as the caldarium. This area was specifically designed to provide patrons with a heated environment that was conducive to relaxation and cleaning. The caldarium typically featured hot water that was heated through a system of hypocausts, which circulated hot air beneath the floors and through the walls. The architecture of the caldarium often included domed ceilings and marble finishes, creating an atmosphere of luxury and comfort.

The other options refer to different chambers within the bath complex: the palaestra was an exercise area, the frigidarium was a cold bath chamber, and the apodyterium served as a changing room. Each of these plays a distinct role within the bathing process, emphasizing the multifunctionality of Roman baths, but it is the caldarium that specifically indicates the hot bathing area.