Excavated ruins found underneath the castle and modern baths. Very interesting to find out how the big complexes were heated. Apparently the whole place was built over a sub-level like the one here, wiith pillars built by cementing tiles together; they had this massive fire going, like in a boiler room, and the heat and smoke created there would drift among these columns and heat the floor above. Then in the walls, they had these hollow bricks; the heat and smoke would go up through the walls via these bricks and up to chimneys, heating the walls in the process. The giant fire was also used to heat the hot water tanks, which were mixed with cold regular water as needed to get whatever temperature water you wanted in any particular room. Anyway, this heating system was apparently very well preserved. Interesting.