The best-preserved Roman bathing complex in northern Europe, and Bath's most visited attraction. The site centres on the Great Bath, a lead-lined pool still filled with steaming green mineral water, surrounded by Roman columns and Victorian additions. The museum below ground level reveals the original Roman engineering: underfloor heating systems, lead pipes, and the temple of Sulis Minerva, the Romano-Celtic goddess who presided over the springs.
Allow at least ninety minutes for the visit, and consider the evening torchlit sessions in summer when the site is atmospheric and far less crowded. Audio guides are included in the ticket price, and the one narrated by Bill Bryson is genuinely entertaining. You can taste the warm mineral water at the Pump Room next door, though fair warning: it is an acquired taste.