The remains of Macroom Castle dominate the town. Probably dating from the reign of King John, the Castle has had an interesting history, passing from conquerer to conqueror over the centuries. In the 17th century, the castle was lost to Cromwell, who gave it as reward to Admiral William Penn. His son, also William Penn went on to found the state of Pennsylvania in America. Today, the castle arch in the town leads to the Castle grounds, with their picturesque wooded riverside walks.