Different challenging tunnel projects in the downtown area of the city of Mainz in Germany are presented. These tunnels run parallel in a distance of 4 m to max. 50 m. The tunnels were built in soft soil conditions consisting of filling, clay and marl layers of the Tertiary. The paper presents the different construction techniques, the calculation methods for the two tunnels as well as the results of measurements for the New Tunnel Mainz. The experience for the construction of this tunnel and the results of the measurements were the basis for the chosen construction and calculation method for the rehabilitation of the Old Tunnel Mainz, which is currently under construction.