The castle was built by William I in 1068. It consists of a motte - a large mound of layers of rammed earth and clay and bailey - a large flat open area surrounded by an embankment, strong timber fence and ditch.

To give the castle extra strong defences William built a dam across the River Foss. This created a large lake called the King's Fishpond. This lake was a significant feature in York for the next 700 years.

The castle was built from earth and wood. This made it an easy target in 1069 when the whole structure was burnt down by the locals who joined with the Danes to engage in a revolt against William. It was quickly rebuilt.
memorial of the Jewish massacre  

In 1190 it was burnt down again. This time by anti-Jewish rioters attempting to massacre a group of local Jews who had taken refuge there. The Jews, however, "chose to die at each others hands" rather than be burnt to death.

There is a memorial commemorating this tragedy at the foot of the mound.