A 2,000-year-old Adena burial mound located along a busy street in Columbus, Ohio.

A retro walk through the history of the tube.

The inventor of a number of hybrid corn species is immortalized with a field of giant corn.

This mural celebrates the early integration of a New Hampshire baseball team.

This collection of grinning ephemera has grown from basement to Brooklyn.

This innocent-looking townhome is actually a subway exit.

A WWI fighter plane and turn-of-the-century penny candy shop are among the unexpected features of this Financial District building.

Volunteer-run library dedicated to exploring five decades of activism history.

Lie in a hammock where George Washington stood.

The crown jewel of the Queens Museum is a nearly 10,000-square-foot architectural model of the city originally built for the 1964 World's Fair.

The factory for the popular Dumbo location, the Greenpoint shop is a quiet gem.

Deep under Manhattan is the largest construction project in city history. So far, the project has taken the lives of 23 workers, or "a man a mile."

A clock set into the concrete outside a Manhattan jeweler has been telling time underfoot for over a century.

A hyper-luxurious, 12,000- square foot home might be buried beneath Queens, still waiting to protect you from nuclear missiles.

This futuristic airport terminal was abandoned for decades before reopening as a hotel—with a vintage plane of its own parked out back.

Prove you deserve to be fed by Kenny Shopsin.

A living archive of urban activism and space reclaimed.

Manhattan's lighthouse, erected at the insistence of the unsinkable Molly Brown.

Once America's longest-manned military fort, now an abandoned hulk.

The end of the 4 Line is also the end of the line for 300,000 souls in one of NYC's most illustrious cemeteries.

New York's oldest and possibly grandest keeper of books.

This iconic tattoo shop has its own onsite museum with artifacts from the early history of modern body art.

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

An arcade packed with a rotating collection of unique independent video games.