Immensee station is considered the starting point of the main line of the Gotthard railway, and official distances to all points south are measured from here. From Immensee, the line follows the Lake of Zug to Arth-Goldau station, at an altitude of . Here it joined by the Zug branch of the Gotthard railways, and there is a junction with the Südostbahn route to Rapperswil and Romanshorn. Connection is also made with the Arth-Rigi-Bahn, a rack railway climbing the mountain Rigi.