"The space is not just like a historical site; it"s become some sort of place of entertainment, excitement," said Lukas Staudinger, co-founder of POLIGONAL, which hosts "exploratory" walking tours of Berlin"s most architecturally significant areas. "It"s a space for sub-cultural practices. It"s a space for many different things, including for certain birds, which only nest there and nowhere else in the whole area."