a rounded, cliffed sandstone headland in the Highland council area, Scotland, that is the northernmost point on the mainland of Great Britain. Dunnet Head is about 3 miles (5 km) across and juts out into the Pentland Firth of the Atlantic Ocean. It forms a plateau at an elevation of about 100 feet (30 metres), with hills rising to 422 feet (129 metres). The headland's northern tip is crowned by a 346-foot- (105-metre-) high lighthouse built in 1831.