The historic building known as the Bishop's Palace was built by the Bishop of Winchester in the 12th and 13th centuries and later became the Manor House.
In 1757, the manor house was acquired by the Duke of Marlborough.
The archaeological remains which are visible are protected from the elements under a modern roof cover.
The site is open from Monday to Friday, 10am-5pm. The interpretation centre is open by appointment only. Admission is free.