Lambert's Castle is an Iron Age hill fort and since 1981 it has been designated as a Site of Special Scientific Interest (SSSI) on account of its geology, archaeology and ecology.

The hill fort is situated on a broad northerly spur at the summit of Lambert's Castle Hill, which rises to a height of 256 metres (840 ft).

Lamberts Castle was built around 2,500 years ago and a prominent ditch and bank still survive near the western entrance. A fair was held here from 1709 to 1947, during which times the hilltop was used as a racecourse.