A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

Dine amidst exotic plants at this former royal greenhouse.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The beautiful baroque library of the Hapsburg empire.

Brightly colored 30-foot-tall totems light up the desert sky just outside Las Vegas.

A book collector's dream, this Toronto bookstore has the world's first "Biblio-Mat," a random book vending machine.

A preserve with 75,000 ancient drawings remains the realm of public – not just scientific – exploration.

One man has carved a number of natural New Mexico caves into psychedelic sandstone temples.

A famous flea market artist's studio that's full of odds and ends.

On the side of a remote mountain, a stone face bearing an inscription of mysterious origin.

Giant origami sculptures tucked into desert scenery beckon passers-by to explore further.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

This abandoned amusement park was built on a site with a dark history.

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

Take a steam-powered ride straight out of the past on this Appalachian rail line.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

A unique geological area spiked with wind-carved rocks that resemble teepees.

A clear blue swimming hole with hidden caves, still unexplored.

The location of the last stand of Charles Manson's doomsday cult.

An artist's vision for connectivity spans seven continents and 16 countries.

This old mining town, deep in the California desert, has a year-round population of one.

Nestled in the heart of San Francisco’s bustling Financial District stands a unique homage to the Mayan and Beaux Arts.