I once had a literature professor who described Bath as "the Jane Austen version of the Hamptons," which feels like a fairly accurate description of this ancient Roman city.
Known for its natural hot springs and Roman baths (the only place in the UK where you can bathe in natural, thermal waters), the entire city of Bath has been deemed a World Heritage Site by UNESCO. Tour the 2,000-year-old bath house, the former Benedictine monastery of Bath Abbey (if Gothic interiors are more your style), and the 14th-century remains of Farleigh Hungerford Castle (found just outside the city limits).
For a more modern spa experience, book a stay at The Royal Crescent's Spa and Bath House (a place any one of Austen's characters would be happy to unwind).