This Luxembourg cave is covered in cryptic looking marks left by mining activity.

This taxidermilogical collection was assembled by a peltmonger turned animal activist.

This small museum displays a collection of outsider art and scale models of past "treatments" for mental illness.

Museum of science fiction, utopias, and extraordinary journeys of the mind.

A mythically themed self-built sculpture park.

For centuries no one knew there were hundreds of bones and precious artwork hidden beneath this Swiss church.

This impressive collection of skulls and bones was gathered by an ex-zookeeper who took advantage of a pig plague.

Housing the groundbreaking maps and globes of Gerard Mercator.

A Museum of Psychiatry in a still-operating mental institution.

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

Lavish royal estate punctuated with heated greenhouses.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

This steel frame is a skeletal mirage of a lost 16th-century stone building.

This massive collection of taxidermy is full of specimens collected by missionaries during their international travels.

A late-medieval Dutch castle with trick fountains in its whimsical water gardens.

The tallest waterfall in the Netherlands is a lovely, stepped feature that is only 50 feet tall.

A seven-century-old jail tells a not-so-pleasant history of crime and punishment.

This museum inside Amsterdam's largest cemetery explores how people deal with death.

This subterranean studio is filled with fascinating kinetic art.

This basement museum explores the art and artistry of fascism.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.