After the restoration of Charles II in 1660, the present 'Ducal Mansion' was built by Henry Cavendish, 2nd Duke of Newcastle between 1674 and 1679 on the foundations of the previous structure. Despite the destruction of the keep and fortifications of the upper bailey, some rock cut cellars and medieval pointed arches survive beneath the mansion, together with a long passage to the bottom of the rock, commonly known as Mortimer's Hole, through which guided tours take place, starting at the Castle and ending at Brewhouse Yard.