This outdoor gallery of graffiti-covered walls pays homage to the past, present, and possible future of street art.

Huge abstract sculptures of the Puerto Rican Flag.

Not to be confused with the iconic New York City skyscraper, this Chicago building is a vibrant hub for artists.

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

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

A grand New York post office that is home to mailman Santas, scraps of postal history, and a pneumatic mail system.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

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

Wine bottle sculpture with a ship's stateroom inside.

New York City's smallest piece of private property.

Macabre astrological automaton clock dating to the late 1400s.

One of the last few places in Manhattan that employed a pneumatic systemic keeps it on display.

Everyone from Mark Twain to Teddy Roosevelt has a pipe hanging from the walls of this historic chophouse.

Named the fifth most beautiful building in America in 1885, this former courthouse boasts the best view in the Village.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

The most confusing clock in New York.

Catacombs turned marketplace.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

Elevated freight railway turned wildly successful urban park.

An artist's cute bronze subway sculptures belie his violent artistic past.

One of only two commuter aerial tramways in the United States.

Storage warehouse of the rich and famous.

Salute the leader of the proletariat.

The greatest real estate coup of all time.