The GBT consists of a large complex with, at its core, two single-track tunnels connecting Erstfeld (Uri) with Bodio (Ticino) and passing below Sedrun (Grisons).

[15] The main purpose of the Gotthard Base Tunnel is to increase local transport capacity through the Alpine barrier, especially for freight on the Rotterdam–Basel–Genoa corridor.

The tunnel is specifically meant to shift freight to trains from trucks, and thereby to reduce environmental damage and deadly road crashes.

The tunnel also provides a faster connection between the canton of Ticino and the rest of Switzerland, as well as between northern and southern Europe, cutting the Basel/Zürich–Lugano–Milan journey time for passenger trains by one hour (and from Lucerne to Bellinzona by 45 minutes).

[5][12] It is also the first flat route through the Alps or any other major mountain range, with a maximum elevation of 549 m (1,801 ft) above sea level,[5] corresponding to that of Bern.

[5] Like the two other tunnels passing below the Gotthard, the Gotthard Base Tunnel connects two Alpine valleys across the Saint-Gotthard Massif: the Urner Reusstal in the canton of Uri, in which flows the river Reuss, and the Valle Leventina, the largest valley in the canton of Ticino, in which the river Ticino flows.

There, the tunnel penetrates the western slopes of the Bälmeten and Chli Windgällen (although only marginally) before passing below the valley of the Chärstelenbach, a creek in the Maderanertal.

For a few kilometres, the tunnel passes below two western tributaries of the Brenno in the Valle Santa Maria before crossing the last range, west of the Passo Predèlp (about 2,500 m (8,200 ft)) and east of Faido.

[21] Quite late, compared to other current top-importance routes through the Alps (e.g. Simplon, San Bernardino, Brenner, Mont Cenis), namely in 1830, the first Saint-Gotthard Pass road was established after centuries-long usage of a bridle path.

From 1842 onwards, a daily course by the Gotthard Post, a stagecoach drawn by five horses with ten seats, still took about 23 hours from Como to Flüelen.

The road between Göschenen and Airolo over the summit of the pass, comporting notably the Schöllenen ravine and the Tremola, had countless hairpin turns and serpentine curves, dropping 1,000 m (3,300 ft) in altitude.

From 1953 onwards, the pass road was sequentially improved and expanded at several sections along the Gotthard route, finally ending in 1977 with the opening of an expressway fully circumventing the Tremola.

Both modern motorway and historic railway rely on heavy rockfall and avalanche protection equipments and are exposed to harsh weather condition in winter.

As early as 1947, engineer Eduard Gruner imagined a two-story base tunnel from Amsteg to Biasca, both rail and road, with a stop at Sedrun, to provide a faster and flatter passage through the Swiss Alps.

Because of ever-increasing international truck traffic, Swiss voters chose a shift in transportation policy in September 1992 by accepting the NRLA proposal.

[6][7][8] At opening the GBT reduced travel times for trans-Alpine train journeys by about 40 minutes, and by one hour when the adjacent Zimmerberg and Ceneri Base Tunnels were completed.

A proposal to construct a functioning railway station, called Porta Alpina (from Romansh, "Alpine Gate"), at this site was evaluated, but the project was put on hold in 2007 and definitively cancelled by the federal authorities in 2012 as uneconomical.

[34][35] On 30 August 2013, the tunnel was entirely traversed for the first time from Bodio to Erstfeld in six hours, by diesel train, buses and by foot.

[36] On 16 December 2013, the operational test phase started on a 13-kilometre (8.1 mi) stretch in the southern section of the west tube between Faido and Bodio.

[38][39] On 1 October 2015, following permission by the Federal Office of Transport, the first tests on the entire length of the GBT were performed, with steadily increasing speed.

[49] In 2016, several events, including festivities and special exhibitions, were held around the Gotthard, culminating in the inaugurations in early June, dubbed Gottardo 2016.

A bronze memorial plaque with their names — four coming from Germany, three from Italy, and one from each of South Africa and Austria – was unveiled by AlpTransit Gotthard AG CEO Renzo Simoni.

The first journey carried hundreds of Swiss citizens who had won tickets in a draw, while the assembled guests in Erstfeld, including the Federal Council in corpore, heads of state and government from neighbouring countries and transport ministers from European countries, attended the opening show Sacre del Gottardo by Volker Hesse featuring 600 dancers, acrobats, singers and musicians celebrating Alpine culture and myths around the Gotthard.

From 2 August to 27 November 2016, the Swiss Federal Railways ran a special train service through the tunnel called "Gottardino" which was open to the public.

According to an SBB press conference, around 8km of tracks, 20,000 concrete sleepers and a lane change gate in the tunnel were severely damaged.

[86][87] Experts from the Swiss Transportation Safety Investigation Board (STSB) were dispatched to the site to preserve and document evidence of the crash.

Originally expected to be completed by the end of 2023, it was announced in November 2023 that the repairs would not be finished before September 2024, with the tunnel operating at reduced capacity until then.

[89] This was due to repairs requiring a complete replacement of seven kilometers of rails, including 20,000 sleeper blocks and their concrete foundations, a damaged lane-change gate, two high-speed switches and many other safety and operationally relevant parts.

[90] Freight trains were allowed to use the east tunnel from 23 August due to a temporary maintenance gate replacing the damaged one whilst passenger services remained rerouted.

[93] Since the opening date on 1 June 2016, between 130 and 160 trains on an average working day operated through the Gotthard Base Tunnel, which in March 2019 marked the 100,000th transit.