Loch Lomond is a freshwater loch lying on the Highland Boundary Fault, often considered the boundary between the lowlands of Central Scotland and the Highlands. It is 39 kilometres (24 mi) long and between 1.21 kilometres (0.75 mi) and 8 kilometres (5.0 mi) wide. It has an average depth of about 37 metres (121 ft), and a maximum depth of about 190 metres (620 ft). Its surface area is 71 km2 (27 sq mi), and it has a volume of 2.6 km3 (0.62 cu mi). Of all lochs and lakes in Great Britain, it is the largest by surface area, and the second largest (after Loch Ness) by water volume.