One of the few places in Britain where you can bathe in natural hot-spring water, and in an open-air rooftop location as well, this striking complex designed by Nicholas Grimshaw consists of a Bath-stone building surrounded by a glass curtain wall. The only difficulty is in deciding where to spend more time—in the sleekly luxurious, light-filled Minerva Bath, with its curves and gentle currents, or in the smaller, open-air rooftop pool for the unique sensation of bathing with views of Bath's operatic skyline (twilight is particularly atmospheric here). Two 18th-century thermal baths, the Cross Bath and the Hot Bath, are back in use too (the latter for treatments only). End your session in the crisp third-floor café and restaurant. It's essential to book spa treatments ahead of time. Towels, robes, and slippers are available for rent. Note that changing rooms are co-ed. Weekdays are the quietest time to visit. You must be 16 to bathe here and 18 to book a spa treatment. A separate, free Visitor Centre (April through October, Monday through Saturday 10–5, Sunday 11–4) opposite the entrance gives an overview of the project and provides audio guides (£2) for a brief tour of the exterior.