Switzerland sees itself as the nation of tunnels par excellence, especially since completion of the Gotthard Base Tunnel - at 57 kilometres, the longest rail tunnel in the world. There are, after all, countless tunnels criss-crossing the nation. Switzerland also built the first tunnel through the Alps - the Urnerloch, in 1708. But the country isn't alone. Some say the world's longest tunnel is in Guangzhou, China: 67 kilometres of it, all for an underground line. The 64-kilometre Brenner Base Tunnel is currently being dug between Austria and Italy. China's Bohai Tunnel, scheduled to open in 2022, is reputed to be 123 kilometres in length.