Glen Roy (Scottish Gaelic: Gleann Ruaidh meaning "red glen") in the Lochaber area of the Highlands of Scotland is a National Nature Reserve and is noted for the geological puzzle of the three roads ("Parallel Roads"). The "Parallel Roads" of Glen Roy are lake terraces that formed along the shorelines of an ancient ice-dammed lake. The lake existed during a brief period (some 900-1,100 years in duration) of climatic deterioration, during a much longer period of deglaciation, subsequent to the last main ice age (The Devensian).