The Lindentunnel is a partially filled tunnel under the boulevard Unter den Linden in the Berlin district of Mitte. Built from 1914 and opened on December 17 and 19, 1916, the tunnel was used by the tramway as an underpass under the boulevard, replacing an at-grade crossing at the same location that had been put into operation in 1894. The tramway used the structure until 1951, after which it was used as a prop warehouse for the Berlin State Opera and as a parking lot for vehicles of the East German People's Police. After German reunification, performance artist Ben Wagin used parts of the tunnel as an exhibition space, while other parts have been used since the 1990s to store props for the Maxim Gorki Theater. Complete demolition of the tunnel is planned in the medium term.