Read a book next to a Midtown waterfall.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

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

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

A miniature rainforest is growing inside of a Midtown Manhattan office building.

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

Try not to get slimed in Tribeca.

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."

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

A terrific purveyor of natural history objects and curios.

Built to power trains, the engines in this building provided the entire city of Madrid with electricity during the Spanish Civil War.

Strange masks and obscure costumes are housed in this old Madrid corrala.

This small museum tucked within a subway station holds pieces from Madrid's past.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

This small and often-overlooked museum holds some of Spain's finest artistic treasures.

Madrid's last horchata kiosk is a blue-and-white beacon of refreshment.

This lucky bronze frog was gifted to Madrid by a casino.

Earth's rocky history has rarely glittered so brightly as it does in this Spanish museum.

The little church's beautifully frescoed ceiling has earned it the nickname “the Sistine Chapel of Madrid.”

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

A whimsical brother of the nearby Fallen Angel statue takes the falling part quite literally.

A lush indoor jungle fills this bustling Madrid transportation hub.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.