Ongar was an important market town in the Medieval era, at the centre of a hundred and has the remains of Ongar Castle, which was a Norman castle built in c. 1086 and demolished between 1558 and 1603. The Church of England parish church, St Martin’s, dates from the 11th century and shows signs of Norman work. A small window in the chancel is believed to indicate the existence of an anchorite’s cell in medieval times. The Gothic Revival architect C. C. Rolfe added the south aisle in 1884. St Andrew’s Parish Church in Greensted, 2 miles (3.2 km) west of Ongar, is believed to be the oldest wooden church in the world.