Construction began on 3 November 1969 on and under Karlsplatz, where three lines of the basic network were to meet, and where central control of the U-Bahn was located.
Pembangunan dimulai pada 3 November 1969 dan dimulai di bawah Karlsplatz, dimana tiga jalur dari jaringan dasar bertemu, dan pusat kontrol dari U-Bahn awalnya berlokasi.