Christ Church College is uniquely a joint foundation of the university and the cathedral of the Oxford diocese, Christ Church Cathedral. The cathedral both serves as the college chapel and its dean is ex officio the college head. The college is amongst the largest and wealthiest of colleges at the University of Oxford. Its grounds contain a number of significant buildings, such as Tom Tower, Tom Quad (the largest quadrangle in Oxford), and the Great Dining Hall, which was the seat of the parliament assembled by King Charles I during the English Civil War. Christ Church sits in approximately 175 acres of land, including Christ Church Meadow, Merton Field and Boathouse Island. In addition Christ Church owns Aston's Eyot (purchased from All Souls College in 1891), Christ Church recreation ground (including the site of Liddell buildings), and School Field which has been leased to Magdalen College School since 1893.