Canterbury is a historic English cathedral city, which lies at the heart of the City of Canterbury, a district of Kent in South East England. It lies on the River Stour. Many historical structures remain in the city, including a city wall founded in Roman times and rebuilt in the 14th century, the ruins of St Augustine's Abbey and a Norman castle, and perhaps the oldest school in England, The King's School. Modern additions include the University of Kent, Canterbury Christ Church University, the Marlowe Theatre, and the St Lawrence Ground, home to Kent County Cricket Club. The city lies at the heart of the City of Canterbury, a local government district.