In typically ostentatious style, the Romans constructed a complex of bathhouses above Bath's three natural hot springs, which emerge at a steady 46°C (115°F). Situated alongside a temple dedicated to the healing goddess Sulis-Minerva, the baths now form one of the best-preserved ancient Roman spas in the world, and are encircled by 18th- and 19th-century buildings. Bath's premier attraction can get very busy. To dodge the worst crowds, avoid weekends, July and August.
The heart of the complex is the Great Bath, a lead-lined pool filled with steaming, geothermally heated water from the so-called 'Sacred Spring' to a depth of 1.6m. Though now open-air, the bath would originally have been covered by a 45m-high, barrel-vaulted roof.
More bathing pools and changing rooms are situated to the east and west, with excavated sections revealing the hypocaust system that heated the bathing rooms. After luxuriating in the baths, Romans would have reinvigorated themselves with a dip in the circular cold-water pool, which now has life-size films of bathers projected on to the walls.
The King's Bath was added sometime during the 12th century around the site of the original Sacred Spring. Every day, 1.5 million litres of hot water still pour into the pool. Beneath the Pump Room are the remains of the Temple of Sulis-Minerva.
There is also a fascinating museum displaying artefacts discovered on the site. Look out for the famous gilded bronze head of Minerva and a striking carved Gorgon's Head, as well as some of the 12,000-odd Roman coins thrown into the spring as votive offerings to the goddess.
The complex of buildings around the baths were built in stages during the 18th and 19th centuries. The two John Woods designed the buildings around the Sacred Spring, while the famous Pump Room was built by their contemporaries, Thomas Baldwin and John Palmer, in neoclassical style, complete with soaring Ionic and Corinthian columns. The building now houses a restaurant which serves a magnificent afternoon tea (£22, or £31 with champagne). You can also sample the spring waters, which were believed in Victorian times to have curative properties. If you're lucky, you might even have music provided by the Pump Room's string trio.
Admission to the Roman Baths includes an audio guide, featuring a commentary in eight languages. One of the English guides is read by bestselling author Bill Bryson. Free hourly guided tours start at the Great Bath. Saver tickets covering the Roman Baths and the Fashion Museum cost adult/child/family £21/11/53.