Short answers, pulled from the story.
Bath was designated a UNESCO World Heritage Site in 1987, in recognition of its international cultural significance. In 2021, it received a second UNESCO designation as part of the Great Spas of Europe, a group of 11 spa towns across 7 countries, making it one of the only places formally recognised twice as a World Heritage Site.
Aquae Sulis is the Latin name given to Bath by the Romans, meaning the waters of Sulis. Sulis was a local British goddess of the hot springs, whom the Romans identified with their own goddess Minerva. The Romans built a temple and bathing complex at the site around AD 60-70, and retained the name Sulis in the town's official title rather than replacing it entirely.
Beau Nash was the master of ceremonies in Bath who presided over the city's social life from 1704 until his death in 1761. He drew up a code of behaviour for public entertainments and managed the social order of what had become one of Britain's most fashionable spa towns. His authority rested on his ability to organise pleasure rather than on hereditary rank.
Bath suffered three air raids between the evening of the 25th of April and the early morning of the 27th of April 1942, carried out by the Luftwaffe as reprisals for RAF raids on the German cities of Lubeck and Rostock. More than 400 people were killed and more than 19,000 buildings were damaged or destroyed, including houses in Royal Crescent, the Circus, and Paragon, as well as the Assembly Rooms.
Jane Austen did not like Bath. She lived there from 1801 to 1806 with her family at four different addresses, and wrote to her sister Cassandra: "It will be two years tomorrow since we left Bath for Clifton, with what happy feelings of escape." Despite this, she set two novels, Northanger Abbey and Persuasion, in the city.
The hot springs originate as rainfall on the Mendip Hills. The rainwater percolates through limestone aquifers to depths of between 9,000 and 14,000 feet, where geothermal energy raises the temperature to between 64 and 96 degrees Celsius. Under pressure, the heated water rises back to the surface through fissures in the limestone, emerging at a temperature of 46 degrees Celsius at a rate of 1,170,000 litres daily from the Pennyquick geological fault.