A bonspiel is a curling tournament, consisting of several games, often held on a weekend. Until the 20th century most bonspiels were held outdoors, on a frozen freshwater loch. Today almost all bonspiels are held indoors on specially prepared artificial ice.

Castle Semple Loch is a 1.5-mile-long (2.5 km) inland freshwater loch at Lochwinnoch in Renfrewshire, Scotland. Originally part of an estate of the same name, it is now administered by Clyde Muirshiel Regional Park as a watersports centre. An RSPB bird sanctuary is located on the loch's southern shore.