Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

A dilapidated dock tells the story of Titanic's missed arrival.

A hands-on traveling collection of the innovative devices of yesteryear.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

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.

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

A semi-scholarly approach to sex.

Elevated freight railway turned wildly successful urban park.

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

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

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

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

A crumbling hospital from the 1850s on Roosevelt Island.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

A terrific purveyor of natural history objects and curios.

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

The burial ground of two kings and a queen is now a calm city park in the middle of bustling Seoul.

A unique structure located on the grounds of one of five grand palaces that were built by the Joseon dynasty.

This cemetery is dedicated to the people who died fighting for democracy in South Korea.

According to legend, those who pray at this statue will also be granted a wish.

This odd museum/art gallery embraces the physiological, zoological, and ethnographic side of sex.

All that remains of an ancient royal palace is a water channel that was used for drinking games.

This human-made pond is part of a Korean palace complex first built in the 7th century.