The Mörtelstein-Asbach railway tunnel (Mörtelstein tunnel) with a Gothic pointed arch was built in 1862 during the construction of the Meckesheim-Neckarelz railway line. It was in operation until the end of the line in 1971. The tunnel was built from two sides, with one missing the middle, which had to be corrected.
In the war years 1939 to 1945 (Second World War), Daimler-Benz also used the train for transporting prisoners to the gypsum tunnels "A8", "Goldfisch" and "Brasse", in which aircraft engines were manufactured underground.
The tunnel is 688 meters long and inaccessible as it has become home to bats. In addition, penetrating water gradually erodes the tunnel. At the west portal (Asbach side) the portal is walled up, whereas it is only barred at the east portal (mortar stone).
The tunnel can be easily reached from Mörtelstein via the former railway line.
There is an information board at the former Mörtelstein train station.