This tiny structure was built by the creator of the Brooklyn Bridge.

The mysterious canine hides atop a drain pipe on the back of the building, some say as a sneaky shoutout to Yale.

The headquarters of a secretive order is also a beautifully-designed park.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

A derelict bit of transportation infrastructure hidden in the woods.

A vertically floating hemlock controls the waves and weather at Crater Lake.

A visionary precursor to the Internet made of index cards.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

The world's largest squirrel statue clutches a pecan bigger than your head.

One man's lifelong obsession with death.

Home of the golf club used by Alan Shepard on the moon, and more artifacts from the sport's history.

The house and graveyard used in the Stephen King spine-chiller.

The eccentric mansion of one the most popular horror authors of modern times.

Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

A Hawaiian stairway to heaven—that you can't climb.

Elevated freight railway turned wildly successful urban park.

Try not to get slimed in Tribeca.

It was once the base for a series of domestic terror attacks.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

Last residence of H.P. Lovecraft featured in his story "The Haunter of the Dark."

Final resting place of one of the classic authors of horror literature.

"the sweltering inhabitants of Charleston and New Orleans, of Madras and Bombay and Calcutta, drink at my well . . . The pure Walden water is mingled with the sacred water of the Ganges."

The rogue roots are gradually consuming some of the historic marble grave markers.