A range of hills extending 16 miles (25 km) southwestwards from a point 3 miles (5 km) southwest of the centre of the city of Edinburgh, the Pentland Hills extend across the City of Edinburgh, West Lothian, Midlothian, South Lanarkshire and the Scottish Borders Council Areas. Comprising 400 million-year-old sandstone and volcanic rocks of Devonian age, the hills rise to a height of 579m (1898 feet) at Scald Law, a mile (1.5 km) northeast of Penicuik. The West Water, Baddinsgill, North Esk, Loganlea, Threipmuir, Harlaw and Glencorse reservoirs supply water to the city of Edinburgh and in 1984 the area was designated as a regional park with headquarters at Boghall Farm. There is an artificial ski slope at Hillend at the north end of the range and a Ministry of Defence training area centred around Castle Law. Much of the land is given over to forestry, sheep farming and grouse moor.