The big attraction in Trier are these Roman baths. Unlike the ones we saw in Bath England, these were not naturally heated. The Romans built a complex series of furnaces and water channels to heat the water and floor.
Pictures can't really capture just how large the ruins are. There are thousands of feet of tunnels. Of course the kids immediately ran off through them and it took forever to find them again. *** The tunnels had originally had a wood floor suspended about 4 feet up. The space below the floors formed water ways for the baths and sewage removal.