Below the keep is The Great Chamber, a stone building that was once one of the castle buildings.
There was a monastery here in the Middle Ages, and the current parish church once served the monks of Christchurch Priory.
The church was begun around 1094 and rebuilt in 1510 in Perpendicular style. At 311 feet in length it is the longest parish church in the country. It was awarded a 5-star rating in Simon Jenkin's book, 'England's Thousand Best Churches'.