The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

A lecture hall sink once used by Einstein and other noted physicists is now regarded as a strange science relic.

A former plague hospital turned medical museum.

For over a century, it was a crucial center of mental health treatment and also the source of many local legends.

Minnesota's oldest and deepest mine is now an underground physics laboratory.

The arboretum whose marshy soil sucked up the dreams of housing developers.

This architectural stunner is one of the few surviving Egyptian Revival theaters in the U.S.