The Roman baths at Bath, England, still steaming after 1,900 years
The only hot spring in Britain. The Romans called the place Aquae Sulis, after the local goddess Sulis, whom they identified with Minerva, and built a temple and bathing complex here from the late 1st century onward.
The Great Bath is the open-air pool in the middle of the site, originally lead-lined and fed straight from the spring at about 46°C. Around it were the usual heated rooms: tepidarium, caldarium, frigidarium, plus a sacred spring where people threw coins and curse tablets asking Sulis Minerva to punish thieves. The Gorgon head in the museum is from the temple pediment: snakes in the beard, wings, and a face that looks more Celtic than Mediterranean.
Worth knowing before you visit: the pool, spring, and lower masonry are Roman. The statues on the terrace, the upper colonnade, and a lot of what you see from street level were added in the Victorian period when the site was excavated and turned into a museum. The water is still too mineral-rich (and historically too contaminated) to swim in.