This little museum is built on a theater that was once a wildly elaborate speakeasy.

The one-stop shop for all of your superhero (or evil arch-nemesis) needs.

A New York garbage depot holds a secret collection of weird and wonderful refuse.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

Elevated freight railway turned wildly successful urban park.

Try not to get slimed in Tribeca.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

A terrific purveyor of natural history objects and curios.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

This landmark jazz venue is the oldest continuously running African-American club in the United States.

An elaborate memorial to a man local legend says died of a broken heart.

This Buffalo museum hides an Art Deco gas station designed by Frank Lloyd Wright.

One of Frank Lloyd Wright's greatest—and favorite—architectural masterpieces was almost lost.

The ruins of a former sanctuary for elite Aztec warriors.

This Aztec structure remained hidden until the demolition of a supermarket exposed the lost temple.

Once home to an aristocratic family and a workers' organization, this intricately tiled building now houses a chain restaurant.

A neo-Gothic temple in central Mexico featuring a labyrinthine network of crypts.

This ceremonial Mexican square looks as though it belongs in a science fiction movie.

This church, buried halfway in lava rock, is all that remains of a Mexican village destroyed by a volcano.