Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

At the United Kingdom's only residential library you can sleep among the books.

A town church once nearly submerged by the damming of a river is now hauntingly visible as the water recedes.

Visitors dip into a variety of pools of what was once ice.

Venice's "Island of the Mad."

Three bridges and one giant canyon make up this fantastic Spanish settlement.

The "World's Largest Underground Business Complex," a 55,000,000-square-foot city underneath Missouri.

A giant pineapple, a symbol of hospitality, and an amazing vacation rental option.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

The mystery of this small, brick pond eluded its possibly only investigator until his death.

An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

A walkable map of the world, made from soil and stone by one man.

Secret Manor, a house full of legends, the least of which is the haunting of long-deceased ladies of pleasure.

The rocky remains of an ancient Greek forest.

Temple complex that once housed the famous statue of Nike.

A spiritual vortex among the red rocks in Sedona.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

These fantastically named natural pools look like something out of a Scottish myth.

This cramped crevasse saw the entire population of its island suffocated inside its depths.

A small sculpture garden that provides a microcosmic representation of California.

The headquarters of a secretive order is also a beautifully-designed park.

The highest peak in the United Kingdom has a history of physics, specters, and a pilgrimage of strange objects.