This hanging crocodile is thought to be the "dragon" that once plagued a Czech city.

Europe's second largest ossuary wasn't discovered until 2001.

Steadily reminding Czechia of its past.

A Jenga-style cylindrical tower of books that appears to go on forever.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Dedicated to the unsung history of human waste.

This artificial cave looks like something out of a fairytale.

Underneath this small church are 15,000 bones, arranged by an obsessive academic.

This quaint museum tells about more than just the birth of Jesus: "betlémy" are an important piece of Czech history.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

A mocking tribute to the past and modern leadership of Prague.

One man's swirling six-acre monument of stone.

The original Uncle Sam was actually a New York meatpacker who is buried under this historic grave.

An encyclopedic collection of mammal penises.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

The summer home of the largest colony of bats in the world.

Spinning silently in the lobby of an Art Deco masterwork is a massive vintage model of the Earth.

Hidden in an ordinary Midtown building is a one-room museum dedicated to the greatest escape artist.

The world's oldest hologram gallery and the labyrinthine laser laboratory of a holography pioneer.

Touching mementoes from those who didn't make it back from World War I still hang in one of New York's oldest bars.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

This unusually shaped mountaintop tower looks like a UFO floating over the city.

Unique house covered in a nightmarish mural of demons, ghosts and monsters.