The link consists of two single-track tunnels connecting Erstfeld (Uri) with Bodio (Ticino) and passing below Sedrun (Graubünden). It is part of the New Railway Link through the Alps (NRLA) project, which also includes the Ceneri Base Tunnel further south (opened on 3 September 2020) and the Lötschberg Base Tunnel on the other main north-south axis. It is referred to as a base tunnel since it bypasses most of the existing Gotthard railway line, a winding mountain route opened in 1882 across the Saint-Gotthard Massif, which was operating at its capacity before the opening of the GBT. The new base tunnel establishes a direct route usable by high-speed rail and heavy freight trains.