This abandoned caretaker's apartment is one of 13 left in the New York Public Library system.

A completely round house designed for the Atomic Age.

This tiny hotel perched atop a 50-foot tower really puts things into perspective.

This red lake 4,000 meters above sea level is home to rare flamingos.

The world's largest wooden trestle stretches across this desert canyon in Anza-Borrego Desert State Park.

The largest geyser field in the southern hemisphere is a spectacular sight.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

This "Palace of Purification" has made many film appearances as a dark and sinister headquarters.

A medieval military street hidden beneath a charming French fishing village.

This unattributed sculpture in Amsterdam is hiding in plain sight.

This collection of unique liquids allows visitors to wander the waters of Iceland's glaciers.

Iceland's only steampunk shop imagines a retro-futuristic world that never was.

This Brazilian town built by Freemasons is full of colonial Masonic architecture and symbolic imagery.

The world's largest kaleidoscope, designed by a 1960s psychedelic artist.

An overlooked collection of over 350,000 artistic works created by psychiatric patients using art therapy.

NYC's legendary underground network for bovine transportation.

Travel through the hidden underbelly of the city in colorful tunnels filled with art and history exhibits.

These passages carved from the Antarctic ice hold strange shrines to the harsh southernmost climes.

The world's largest neutrino telescope searches for secrets of the universe at the South Pole.

This enormous storm barrier is one of the largest moving structures on Earth, with each arm taller than the Washington Monument.

The Netherlands is home to a bridge printed out of reinforced concrete.

This quiet park's strange sedimentary spires were named after Kodak's color film.

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

A terrific purveyor of natural history objects and curios.