Built in 1788, this is the most complete Georgian playhouse in Britain. It closed in 1848 and was used as an auction house into the early 20th century, reopening as a working theatre again in 1963 after a period of restoration. Fascinating tours (starting on the hour) include a look at the country's oldest surviving stage scenery, painted between 1818 and 1836.
Check the website for upcoming plays and performances; the Christmas pantomime is particularly popular.