Underfloor Heating at Roman Baths

I'm staying in Bath for a few days with my family including my parents, brother and sister in law. We had a lovely day: lunch in The Pump Room, tour of the Roman Baths and relaxation in the Thermae Baths followed by a fantasic dinner at Acorn Vegetarian.
This photo is of the pillars that were an integral part of the underfloor heating of the Roman baths. Perhaps oddly, I like the pattern.