Bolsover Castle is in the town of Bolsover, in the north-east of the English county of Derbyshire. Built in the early 17th century, the present castle lies on the earthworks and ruins of the 12th-century medieval castle; the first structure of the present castle was built between 1612 and 1617 by Sir Charles Cavendish. The site is now in the care of the English Heritage charity, as both a Grade I listed building and a Scheduled Ancient Monument.