Manhattan's Thirteenth Avenue was made on landfill then deliberately destroyed — apart from one small, obscure block.

A trove of century-old litho stones from the Puck Building's printing days were discovered behind a cellar wall, and are now hanging in the store.

The walls are decorated with whimsical murals painted by the creator of the Madeline franchise.

This Manhattan skyscraper is a reminder of the brief but glorious age of urban air taxis.

These ornate manhole covers were used for a now-forgotten purpose.

A forgotten relic from New York's bygone trolley system hides in plain sight under a bridge.

The last living thing to come out of the rubble after 9/11 is now a symbol of hope and resilience.

Creating this diorama spurred naturalist Carl Akeley to begin advocating to protect the apes.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

Look closely and you’ll notice that the color changes a third of the way up the tower.

An overlooked memorial honoring the local Washington residents who died in World War I.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The "lovely red Vega" of the legendary record-settling pilot.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

A retired subway car stands alone in a field in the middle of Queens.

Colloquially known as “piss alley,” this narrow street filled with tiny bars and barbecue stands looks like it was pulled straight out of “Blade Runner.”

Also known as the Blue Church, the building was consecrated to the daughter of Andrew II.

Imagine having a street run right through your home, or better yet, a historic bridge three stories high.

This whimsical fountain pays tribute to Toronto's four-legged friends.

This modest plaza in Moneygall, Ireland has cashed in on its distant connection to the U.S. president.

A hugely vast Irish landscape of barren rock that stretches for miles.

After it was swallowed by a Georgian mansion, this medieval castle remained forgotten for centuries.

Travel deep inside of Europe's second largest glacier in the world's largest man-made ice cave.

This natural rock formation features seemingly unnatural vertical ridges that have been blamed on elves.