An unfinished tomb carved into a giant boulder in the Arabian Desert.

A labyrinthine underworld of tunnels and caverns hides beneath the city.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

The first ever diner included on the National Register of Historic Places is famous for its custard French toast.

Through the colossal entrance to this cave you'll find limestone tubs and an underground waterfall.

Some of New York's best tacos can be found in the back of an unassuming bodega in Queens.

Inside this curiosity shop, visitors can peruse the clown collection or purchase a molar from the mouth of Bigfoot.

In the middle of a remote desert town is a surprisingly opulent hotel.

Millions of glowing microscopic organisms light up the waters of this luminous lagoon.

Cavernous opening completely encased in Karst limestone.

This once-forgotten oasis in the middle of Lisbon was first created over a century ago quite by accident.

This sprawling bookstore spans four floors and has more than a million books in stock.

A once popular resort—said to be the vacation spot of gangster Al Capone—now remains abandoned in the woods of Arizona.

Mexico City's largest market contains a Willy Wonka-esque wonderland.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

An abandoned hotel in the highlands of Bali is shrouded in stories of ghosts, curses, and corruption.

Hidden amid the tropical forest in the Caribbean Sea are the decaying ruins of the Cocaine King's luxurious island party home.

Japan's largest area of "pink moss" turns the hillside bright pink every spring.

This little slice of the Netherlands in the Pacific Northwest blooms in a rainbow of color each spring.

Gorgeous purple flowers drape from the world's largest blossoming plant.

Gnarled canopies of pink and purple wildflowers arch over the trail to the summit.

The space-age building is home to one of the few remaining rotating restaurants in America, and the only one that inspired a 1980s sitcom.

A preposterously luxurious hotel with gold-plated iPads, Rolls Royce chauffeurs, and a staff that trains by watching "Downton Abbey."