The frigidarium was the room patrons entered after taking a warm bath in the tepidarium and a hot bath in the caldarium. Its purpose was to close the pores. In order to do this, the bath was very cold. This is the final bath taken in the complex.

This method of closing the pores is similar to that in the Scandinavian cultures (as well as the cultures of a few other countries with cold climates). Some people do this by sitting in a sauna (much like the caldarium) and later going out and running in the snow, wearing little or no clothes. The thinking behind this custom is that by running in the cold, their pores would close and their skin would be prepared for the cold climate in which they lived.

Fig 1. Japanese men bathe in water that is 6 degrees Celsius for strong, healthy bodies

Image courtesy of: http://www.ki-aikido.com.sg/Ki-Aikido-Gallery1997.html