A famous songsmith's custom piano, dubbed "High Society," is hidden just out of sight in one of New York's finest hotels.

Slyly buy a shake in the Parker Meridien lobby.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

A staggering collection of photographs depicting medical, social, and historical change.

This semi-hidden Manhattan restaurant is based out of a loading dock.

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

Hidden in an ordinary Midtown building is a one-room museum dedicated to the greatest escape artist.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

Eat a Nobel banquet from any year in the basement of Stockholm's City Hall.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

You don't have to be an ambassador to dine like one.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

This electric green sulphur lake in New Zealand looks like a cartoonish radioactive dump site.

Hidden deep in a forest is this geological wonder carved by glaciers.

A magnificent waterfall is also home to the remains of a Roman hydraulic engineering system.

What appears to be an ordinary bridge is actually a rare aqueduct.

Visitors can explore the role of mysticism throughout the ages inside this interactive museum of magic.

This tangled English forest looks like something right out of a fairytale.

If there's another drive-through golf-cart bar in a bat-filled cave on top of a mountain, we don't know about it.

The ancient settlement attracts tourists from all over looking to learn about the Chinese vision of the afterlife.

This ancient sword lay in a waterlogged tomb for 2,500 years, but managed to remain relatively untarnished and impressively sharp.

The ritual has been performed uninterrupted for nearly 700 years.