town and district, administrative and historic county of Derbyshire, England. The district takes its name from the principal town in an area of agricultural land interspersed with small coal-mining settlements. The district's administrative headquarters are in Bolsover town. One of Britain's major smokeless fuel plants is located at Bolsover. New industries have been sought to compensate for the contraction of coal-mining employment in the locality. Important remnants of the preindustrial era include the 17th-century Bolsover Castle, which commands the River Doe Lea valley. Hardwick Hall, which was built in the late 16th century by Elizabeth, dowager countess of Shrewsbury (Bess of Hardwick), is now the property of the National Trust. Area district, 62 square miles (160 square km). Pop. (2001) town, 11,291; district, 71,764.