A Caldarium (also called a Calidarium, Cella Caldaria or Cella Coctilium) was a room with a hot plunge bath, used in a Roman bath complex.
This was a very hot and steamy room heated by a hypocaust, an underfloor heating system. This was the hottest room in the regular sequence of bathing rooms; after the caldarium, bathers would progress back through the tepidarium to the frigidarium.
In the caldarium there would be a bath (alveus, piscina calida or solium) of hot water sunk into the floor and there was sometimes even a laconicum - a hot, dry area for inducing sweating.
The bath's patrons would use olive oil to cleanse themselves by applying it to their bodies and using a strigil to remove the excess.
caldarium in Spanish: Caldarium
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caldarium in Swedish: Caldarium