Beyond being incredibly fun, not much can be said about the Hole with certitude.

Site of a former hidden treehouse in New Orleans.

Remnants of a storybook amusement park hidden behind a strip mall.

A century-old network of freight tunnels underneath the city's historic business district.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

Tucked away down this Baytown alley exists a one-of-a-kind art exhibit of technicolor umbrellas.

The oldest original lighthouse in Alaska that was born out of a tragic shipwreck.

This historic Ohio bridge is adorned with fanciful locks left behind by loving couples.

This large Sitka spruce that appears to be floating in mid-air, has defied logic for years.

The isolated final resting place for perished coal miners.

A historic lighthouse steeped in rumors of ghost and pirate stories.

Mariners once used this prehistoric landfill as a navigational landmark.

This abandoned train tunnel has been the subject of countless ghost stories for years.

A beautiful, water-filled quarry that has become a popular haunt for swimmers and artists.

Featuring the the longest lift span of any vertical-lift bridge in the world.

This ruined quarry once produced the distinctive red sandstone used for construction projects in Washington, D.C.

This small island was the first National Wildlife Refuge ever created in the United States.

The longest structure of its kind ever built in Michigan.

This winding road of 318 curves is a must-visit for (careful) motorcycle and sports car enthusiasts.

An ADA-accessible trail and deck offering stunning views of Colorado’s Mount of the Holy Cross.

Alexander Hamilton’s creation caused quite a bit of controversy.

A collection of birdhouses await curious motorists and avian squatters.

At the base of Steens Mountain resides an otherworldly desert.

A massive bur oak tree believed to be some 500 years old is the centerpiece of this quiet urban greenspace.