How do mountain passes shape travel and trade?

A mountain pass is a gap or saddle between higher peaks that offers a relatively easier crossing through rugged terrain. Because climbing over a pass is usually easier than going around a whole range, passes have long guided caravan routes, railways, and modern highways. Famous historical passes such as the Khyber Pass have connected regions for centuries, while Alpine passes helped shape trade across Europe. Weather, snow, and altitude can make passes difficult or dangerous, so many are seasonal or require tunnels and switchbacks. Their geography has had a major influence on settlement, warfare, and commerce.