It passes under the Zürichberg range of hills that separates Zürich city centre from the Glattal region.

The tunnel incorporated a set of underground platforms at Stettbach station, and carries twin standard gauge (1,435 mm or 4 ft 8+1⁄2 in) tracks electrified at 15 kV AC 16,7 Hz using overhead line.

Prior to these changes, Zürich Hauptbahnhof was a west-facing terminal station that required through trains to reverse in its platforms.

Trains to and from the Lake Zürich right bank line had to traverse a 5 km (3.1 mi) long 270° curve to reach Stadelhofen station, whilst trains to and from the north and east were forced to use a rather indirect route through Zürich Oerlikon station.

To the east of Stettbach new links were constructed, linking to the Zürich to Winterthur line at Dietlikon station, and to the Wallisellen to Rapperswil line at Dübendorf station, thus allowing trains to take a direct route to and from the east and north of Zürich.