DOVER, England – The plaque on the side of the Keep at Dover Castle notes it was built by King Henry II from 1181 to 1188. Despite being more than 800 years old, the Keep is far from being the oldest structure at Dover Castle. The castle has a Roman pharos, or lighthouse, which was probably built in the first century A.D. (U.S. Air Force photo/Staff Sgt. Stephen Linch)