An uber-secure, windowless tower of doom in the center of Manhattan is an NSA spyscraper.

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

This anonymous businessman sculpted in bronze became an enduring memorial after 9/11, and had been mistaken by rescue workers for a survivor in the rubble.

Unrepaired walls from a 1920 anarchist bomb attack.

A masterpiece of LGBT art has been restored in what may now be the most valuable restroom in America.

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

A Rocky Mountain city provides a happy ending for a pinto pony and his Brobdingnagian red chair.

This museum offers an actual time machine back through Colorado's past.

Even for Egyptian royalty, the afterlife was bring-your-own-beef.

Once thought to be the fabled Holy Grail, it is now known to be an oil lamp.

Curious crustaceans support an obelisk from ancient Egypt that now stands in modern-day Central Park.

A 19th-century politician who died after walking home in a blizzard is honored with this Manhattan statue.

The rough and tumble president's childhood home displays the shirt he was once shot in and the speech that saved him.

The walls of America's oldest masonry fort famously "swallowed" cannonballs.

The remnants of the fortress that saved Georgia from the Spanish still stand guard on their swampy island.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

A gothic palace of endless stalagmites and pseudoscorpions waits within one of the world's most beautiful caves.

A precariously balanced rock perches on the edge of a cliff created tens of thousands of years ago by glacial erosion.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

Once connected to the outside world by a single train track, this ghost town is looked after by the National Park Service.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

Knoxville’s architectural icon was the symbol of the 1982 World’s Fair, even catching the googly eye of Bart Simpson.

Enormous lake at the bottom of a unique cave system.

A failed utopian experiment for British expats in the American South is now a Victorian village frozen in time.