"Battle Abbey was founded by William the Conqueror to commemorate the battle of Hastings and to fulfill his vow to erect such a monastery should he obtain the victory in that decisive fight. The foundation was dedicated to St Martin, and the building was placed upon the rising ground which looks down upon the rolling valleys which slope southwards towards the bay of Hastings. It occupies the classic site of Senlac, where the last stand was made by the English under Harold, on the memorable day of the battle of Hastings, October 14, 1066."
Extract from "The Greater Abbeys of England" (Open Library).
Battle Abbey is a English Heritage property with free entry for English Heritage members.