Complex sentence: In recent years, the part of the tunnel was turned into an unofficial mausoleum-like site by citizens of Warsaw and in 2001 the Polish parliament Sejm appealed for construction of an official memorial at the tunnel.
Split into simpler sentences: In recent years, the part of the tunnel was turned into an unofficial mausoleum site by citizens of Warsaw. In 2001 the Polish parliament Sejm appealed for construction of an official memorial at the tunnel.