mountain pass in southern Switzerland between the Pennine and Lepontine Alps at 6,581 ft (2,006 m) on the watershed between a north-flowing tributary of the Rhône and a south-flowing tributary of the Toce. It was not until the mid-13th century that the pass attained any importance as a route, and it was only when Napoleon (Napoleon I) built (1800–07) a carriage road through the Gorge of Gondo that the pass began to compete with the other Alpine passes as a major link between central and southern Europe. Near the summit of the pass is a hospice, first mentioned in 1235 as in the charge of the Order of St. John; it is now occupied by the Augustinians. A railway tunnel (Simplon Tunnel) 12.5 mi (20 km) long (opened 1906) cuts through 4,285 ft beneath the pass and connects Brig, Switz., with Iselle, Italy.