The Gotthard Base Tunnel, with a length of and a total of of tunnels, shafts and passages, is the longest railway tunnel in the world, with a geodetic distance of between the two portals. It is also the first flat route through the Alps or any other major mountain range, with a maximum height of above sea level, corresponding to that of Bern. It is the deepest railway tunnel in the world, with a maximum depth of , comparable to that of the deepest mines on Earth. Without ventilation, the temperature inside the mountain reaches .