Clifford's Tower, York, North Yorkshire, England

The mound on which the ruin of Clifford's Tower now stands was thrown up hurriedly by William the Conqueror two years after the Battle of Hastings in order to control the north of England. Several wooden castles have sat on the site before the present building was built between 1244 and 1270 by King Henry III. In 1684, a fire set off a series of explosions that blew off the roof of the building leaving it as we see it today. In 1596, it narrowly survived being demolished by the jailer Robert Redhead. He intended to burn the masonry for lime, but locals stopped him in his tracks by petitioning the government. These days, the distinctive building is open to the public daily and a walk along the top of its walls allows views of the city not possible elsewhere.