A prominent summit of the Upper Clyde Valley, Quothquan Law rises to 335m (1099 feet) a mile (1.5 km) east of Thankerton and 3 miles (5 km) west of Biggar in South Lanarkshire. The River Clyde swings around the hill to the west and its top is occupied by the remains of an Iron-Age hill fort which comprises two enclosures delimited by ramparts.