The Khyber Pass is 33 miles long, 600 to 1,000 feet high and ranges from 600 feet to over a mile wide. The pass includes a caravan track as well as a railroad, which opened in 1925.
The Khyber Pass is of enormous strategic importance, as it is one of the only easy ways through the Spin Ghar mountain range that separates Afghanistan and Pakistan. The path traces a gorge through these mountains that was formed by the passage of two streams.
The pass has offered a route for invading military forces for thousands of years. Darius I of Persia brought his armies through the pass in the 5th century, and Alexander the Great is thought to have used this pass as his troops marched through the region.