Międzyrzecz

A town of 18,691 people (2007), the seat of Międzyrzecz County, Lubusz Voivodeship. It is famous for the nearby Międzyrzecz Fortification Region, a fortified military defense line built in 1934-1938 by Nazi Germany, consisting of around 100 concrete defense structures partially interconnected by a network of underground tunnels. Today, these tunnels form the largest European underground bats refuge, giving shelter to some 32,000 bats of 12 species in the wintertime.