Mountain pass

A mountain pass is a relatively low route through a ridge or mountain range, allowing travel between valleys or regions on opposite sides.

Khyber Pass: A historic mountain pass connecting Afghanistan and Pakistan through the eastern Hindu Kush. Its position made it a major corridor for armies and trade between Central and South Asia.
Mountain saddle: A low point between two higher elevations along a ridge. A pass often occupies this saddle-shaped break in a ridge.
Brenner Pass: An Alpine pass between Austria and Italy, crossed by major road and rail routes. Its comparatively low elevation supports one of the busiest north–south crossings of the Alps.
Mountain tunnel: An underground passage excavated through a mountain for transport or utilities. A tunnel crosses beneath a ridge rather than following a surface route over its low point.
Simplon Pass: An Alpine pass linking the Rhône valley in Switzerland with northern Italy. Its road and tunnel show how engineering can make a high route usable year-round.
Watershed: A boundary separating drainage basins, from which water flows into different river systems. Many passes cross a watershed divide between neighboring valleys.
Great St Bernard Pass: A high Alpine pass between Switzerland and Italy, historically used by travelers and armies. Its hospice became known for sheltering travelers crossing a hazardous route.
Mountain gap: A low opening or break between mountains that permits movement through a range. The broader term can describe a natural corridor without requiring a distinct ridge saddle.
Silk Road: A network of trade routes connecting East Asia with the Mediterranean world. Mountain passes formed essential links along several overland branches of this trade network.
Glacial erosion: The wearing away and reshaping of land by moving glacier ice and its debris. Glaciers can deepen cols and valleys that later become routes through mountain terrain.

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