In which country of the UK is Bolsover Castle?

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.

The building of the castle was continued by Cavendish's two sons, William and John, who were influenced by the Italian-inspired work of the architect Inigo Jones. The tower, known today as the 'Little Castle', was completed around 1621. Construction was interrupted by the Civil Wars of 1642 to 1651, during which the castle was taken by the Parliamentarians, who slighted it, when it fell into a ruinous state.

William Cavendish, who was created Marquess of Newcastle in 1643 and Duke of Newcastle-upon-Tyne in 1665, added a new hall and staterooms to the Terrace Range, and by the time of his death in 1676 the castle had been restored to good order. The main usage of the building extended over twenty years, and it is presumed that the family lived at the castle towards the end of that period.

After 1883, the castle was uninhabited, and in 1945 it was given to the nation by William Cavendish-Bentinck, 7th Duke of Portland.