Brenner Base Tunnel - World's longest underground railway connection: 64km

Brenner Base Tunnel - World's longest underground railway connection: 64km We were delighted to visit the Isarco and Mules construction sites of the Brenner Base Tunnel (Galleria di Base del Brennero) in Italy. When complete, the project will be the world's longest underground railway connection (64km) connecting Fortezza in Italy to Innsbruck in Austria under the Alps. The project is part of the railway corridor connecting Scandinavia to the Mediterranean.