Tour du Mont Blanc A mountain pass is a route through a mountain range or over a ridge. If following the lowest possible route, a pass is locally the highest point on that route. Since many of the world’s mountain ranges have presented formidable barriers to travel, passes have been important since before recorded history, and have played a key role in trade, war, and migration. Mountain passes make use of a gap, saddle or col (also sometimes a notch, hause, bwlch, brennig or bealach, the low point in a ridge.