Over 2800 Years ago, the celts built a shrineto the goddess Sulis where they discovered fissures in the ground at Bath ejecting hot water. Here hot water rises at the rate of 1,170,000 litres per day. The water begins as rain on the nearby Mendip Hills, then filters down through the limestone to a depth of over 4300 metres, before being heated by geothermal activity and rising once again to the surface at a temperature of between 69 and 96ºC. Evidence has been found that during the Roman occupation of Britain, oak piles were driven into the ground to shore up the sides of the hole and later in the 2nd century a building was erected containing three baths — a caldarium, a tepidarium and a frigidarium. This was destroyed in the 6th century, and since then various buildings occupied the site until a new complex was built in the 18th century, which remains to this day. The Roman Baths are open daily and a visit allows you to walk the ancient pavements, just as the Romans did 2000 years ago. As well as the baths themselves, there are extensive remains of the ancient heated rooms, the changing rooms and the tepid and plunge pools. An interactive museum tells the detailed history of the baths and surrounding area.