Here are just 11 of those buildings, which date back to the 11th century.
9. Lewes Castle
Lewes Castle is a Norman Castle built after the Battle of Hastings by supporters of William the Conqueror. The top of The Keep offers stunning panoramic views across Sussex. Photo: Sussex Past
10. Michelham Priory
Michelham Priory is a Tudor house set on a picturesque moated island. It was founded by Augustinian canons in 1229 and the site is steeped in history. Photo: Sussex Past
11. Petworth House and Park
Inspired by Baroque palaces of Europe, the 17th-century Petworth House has been created by one family over 900 years. Photo: National Trust / John Mil
12. Royal Pavilion
The Royal Pavilion was constructed as the seaside pleasure palace of King George IV but it has seen many twists and turns throughout its long history. Photo: Elaine Hammond