The Bohinj Railway is a single-track Habsburg-era line that connects the Sava and Soca valleys through one of the longest railway tunnels in the Alps. The Bohinj station (Bohinjska Bistrica) is a few kilometres east of the lake and worth visiting in its own right: a handsome stone station building from 1906, more or less unchanged.
The most interesting trip is the auto-train, which carries cars (and passengers on foot) through the 6.3-kilometre Bohinj Tunnel to Most na Soci in the Soca Valley — a 25-minute ride that saves a long mountain drive. From there you can carry on to Kobarid, Bovec and the upper Soca, or simply enjoy the scenery and come back on the next train.