Lomond, Loch (lŏkh lōˈmənd, –mən) [key], largest freshwater lake in Great Britain, 23 mi (37 km) long and from 1 to 5 mi (1.6–8.1 km) wide, in Argyll and Bute, West Dunbartonshire, and Stirling, W Scotland. The Leven River drains it into the Clyde. At the southern end of the lake, near its outlet, are numerous wooded islands. The northern end is overlooked by Ben Lomond (3,192 ft/973 m high). The hydroelectric power plant at the northwestern end of the lake is fed by water from Loch Sloy. Loch Lomond has numerous associations with Rob Roy, and a cave there was once used as a refuge by Robert I. The lake is a popular tourist attraction; it and surrounding areas are in Loch Lomond and the Trossachs National Park.