Tintagel Castle in Cornwall is steeped in legend and mystery; said to be the birthplace of King Arthur. The castle also features in the tale of Tristan and Isolde and has a history stretching as far back as the Romans. (http://www.english-heritage.org.uk)
Dover Castle, Kent - one of the best castles I have visited and so much history.....used through WWII for many different purposes......there are 4 miles of underground tunnels that were used as a hospital during WWII.....built on the White Cliffs of Dover
The cliffs above the beach are a noted source of fossils from the Jurassic period. Fossil-hunters walk the beaches between Lyme Regis and Charmouth, but have to be wary of tides and landslips. The Dorset and East Devon Coast World Heritage Site covers 3 geological time periods; the Triassic, Jurassic and Cretaceous. These are showcased in the 3 rock types found along the coast.
Deal Castle, UK is a 16th century coastal artillery fort built by Henry VIII. Deal Castle is built of Kentish ragstone brick, and Caen stone taken from nearby religious houses after the Dissolution of the Monasteries. Whether by design or coincidence, the fortress is shaped like a Tudor rose.