Stuttgart mayor Arnulf Klett, in a letter to Deutsche Reichsbahn dated 11 July 1949, proposed the construction of a tunnel, roughly 1.2 kilometres in length, to run between Central station and Alter Postplatz, just south of Rotebühlplatz; he also mentioned the willingness to undertake financial participation in the project by the city of Stuttgart.

The initial plans envisioned an extension of that line to the Stuttgart–Horb railway, which would also offer faster connections to commuters in the area to the south and southwest of Stuttgart.

To achieve this, a tunnel with a grade of 50 ‰ was planned, which would have connected to the Stuttgart–Horb railway just before the former station at Wildpark, and units of DB Class ET 30 were slated for service.

A new, four-track subterranean station, called Stadtmitte (city centre), was planned to be built underneath the then-under-construction Theodor-Heuss-Strasse, where half of the trains originating at Hauptbahnhof would have turned around.

These changes now enabled the Bundesbahn to develop the plan for the Verbindungsbahn as it was later realized: In May 1971, construction began to build the three subterranean levels for the Klett-Passage for pedestrians, the Stadtbahn, and the S-Bahn.

For this reason, a makeshift platform was constructed at the north-westerly track 1a, and the excavation pit was split lengthwise into two lateral pieces.

Construction was done utilizing the cut-and-cover top-down method, where the outer shell was made up of a 28-metre-deep bored pile wall, on top of which the roof structure of the tunnel was built.

On the topmost internal level, an underground parking garage with 120 spaces was built, which doubled as a civilian shelter, secure against airborne agents, such as poison gas, and nuclear attack, with a capacity for 4,500 persons.

[3][page needed] The technically most challenging aspect of the construction of the Verbindungsbahn was thought to be the subterranean section, 74.6 metres long and about 25 meters wide, underneath the main building of the Hauptbahnhof, which is a protected cultural monument, in the area under the Kleine Schalterhalle (small counter hall).

The platform area was also built to be able to serve as a civilian shelter with a capacity for 4,500 people, which would be usable in case of an emergency if the S-Bahn traffic was also stopped.

The western entrance to a pedestrian tunnel under the Rotebühlplatz was constructed in the inner courtyard of a new building for the Allgemeine Rentenanstalt, a public pensions institution.

The Feuersee, a lake which had been built in 1701, and borders both the excavation zone as well as the Johanneskirche, was drained of all but half a metre of water during the construction phase.

For this reason, and because the thin vertical cover in the area, the rock above the tunnel roof ridge was stabilized by artificially freezing the ground water (Bodenvereisung).

In the rear of the terminal loop section, undepleted anhydrite posed different problems, because this mineral, when it comes in contact with water, tends to massively expand, which puts enormous pressure on the tunnel structure.

Above the Verbindungsbahn, the two streets Lautenschlagerstrasse and Theodor-Heuss-Strasse were opened again for surface traffic in April 1977, to coincide with the Bundesgartenschau in Stuttgart that year.

At the Heslacher Wand access point, a loading track was operated to assist in the removal of 180,000 cubic metres of excavation material from the site.

Once the Verbindungsbahn was put into service, these access points serve as emergency exits, ventilation shafts, and smoke funnels in case of fire.

The tunnel is very close to the building developments on the surface before emerging, and a shock-absorbing system (Masse-Feder-System) is utilized to minimize the ground vibrations caused by the trains.

[3][page needed] As part of the project Stuttgart 21, the S-Bahn tracks between Hauptbahnhof and Bad Cannstatt are scheduled to be renewed and expanded.