Ferropolis (Iron City) is an open-air museum featuring huge industrial machines that are no longer in service. It has been open to the public in Gräfenhainichen, Germany, since 1995. If you can't get there, see some awesome pictures at Socks Studio. Link -via the Presurfer
Previously: After visiting this museum, you'll want to go to Männerspielplatz, the "men's playground."