Monmouth Castle was originally a large 11th century earth and timber ringwork fortress, founded by William fitz Osborn. In the 12th century, the Breton Lords founded the stone castle but sadly only fragments of the curtain wall and ditch, the Great Tower and 13th century Great Hall remain. In the 14th century, John of Gaunt transformed the upper storey of the Great Tower and in 1387 its was the birthplace of his grandson, Henry V. The Great Round Tower of 1230, was demolished during Civil War slighting, with the Marquis of Worcester building the Great Castle House in its place. A medieval fortified bridge guards the crossing of the River Monnow. A mile north-east is Dixton Mound and 5 miles north-west is Newcastle Castle.