On a clear day, you can see all the way to the Virgin Islands from the top of this observation tower built in the 1960s.

A monolith replica monument of Jean Ribault commemorating the landing of the French in the New World.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

The world-record holder for the longest bridge stretching continuously over water.

A rural colonial settlement that contains the remains of a store and cooper.

The last remains of one of the oldest and largest oak trees in the United States calls this state park home.

The glowing blue Nymphaeum of Emperor Tiberius.

This clifftop arch is a natural stunner.

Dedicated to the three priests whose execution inspired author José Rizal.

This saltwater swimming pool, which is the last of its kind in the United States, is slowly crumbling within sight of multiple high-end beachside hotels.

Hiding in plane sight.

This site is home to ancient petroglyphs and pictographs dating back to 6,000 B.C.

The oldest standing structure in downtown San Diego.

L. Frank Baum wrote part of the "Wizard of Oz" series in this wooden Victorian beach resort.

The illuminated falls are a gem in North Cascades National Park.

This sci-fi gazebo located in a Washington power town is made from old bits of industrial electrical equipment.

This raised bulls-eye visible from space was the subject of an intense geologic controversy.

Come for the speed, leave in love with the desert.

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

A statue honoring 44 continuous years of greeting passing ships.

This kitschy tavern is also home to rare early editions of "Treasure Island."

This shale formation along the Appalachian Trail once inspired the third president of the United States.

Bizarre Cavern.

The Cold War-era "underground Pentagon" is a sprawling subterranean hideaway for the Defense Department.