The remains of the 12th century castle are dominated by the 100 ft high circular keep, which is supported by six buttresses. In the mid-1990s, the keep was restored, with a wooden roof and two floors rebuilt. Audio and visual displays now help reconstruct a view of life in a medieval castle, while a history of the site is documented in the adjacent visitors' centre.
The castle was probably built by Hamelin Plantagenet and it was the inspiration for Walter Scott's Ivanhoe. The building is considered South Yorkshire's primary tourist attraction, and sees in excess of 30,000 visitors per year. It is administered by English Heritage.