Clifford's Tower is the motte of a motte and bailey castle, and is all that remains of that castle.
The original motte and bailey castle on this site was erected on the instructions of William the Conqueror.
This building stood for just over a century before being burnt down in one of York’s bloodiest and tragic moments, when, in 1190, 150 Jews were massacred on the site.
The present tower was built between 1245 and 1262 by order of King Henry 111. It was encircled by a moat fed from the River Foss. By 1800, the moat was no longer in existence. The tower was taken within the confines of the new York County Prison which was built in 1826 and demolished in 1935. The tower is now in the care of English Heritage.
@bobhuegel Thanks Bob. In Ian's picture you can see how tall a mound it is on. There used to be a big firework display there on Nov 5th until they found it was spoiling the brick work. Katharine