Simplon Tunnel
The Apennine Base Tunnel, alternatively known as the Grand Apennine Tunnel, is a railway base tunnel 18.507 km (11.5 miles) long on the Bologna-Florence Direttissima line in central Italy. At the time of its completion, the Apennine Base Tunnel was the world's second longest tunnel after the Simplon Tunnel, and the longest built with double track; presently, it is the 16th longest tunnel in the world.