This great stone castle was founded in the early 13th century and became the principle residence of the Kildare branch of the Geraldines. The Kildare FitzGeralds emerged as one of the most power families in Ireland with Maynooth Castle being one of the largest and richest Earl's houses. The original Keep, constructed c.1203, was one of the largest of its kind in Ireland. There is an exhibition on the history of the castle and the family in the Keep.