The Icelandic Sea Monster Museum explores the area's history of aquatic cryptid sightings.

Atlanta's strange assortment of concrete pillars inspires reflection in some, confusion in others.

This abandoned seaside fortress is now simply an imposing ruin being taken back by nature.

The near loss of the stately fireplaces at this medieval castle spawned some of Britain's most crucial historic preservation laws.

A 98-room castle in the middle of Toronto that bankrupted a 19th century electricity multimillionaire.

The abandoned "Ghost Mansion" was left to decay in the mountains of Northern Italy.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

A building shaped like the Army Corps of Engineers logo, because why not?

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

The national park was once a plantation estate.

This lovely pocket park is one of the most under appreciated in D.C.

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

People escaping slavery may have hidden inside a corpse vault.

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

The walls of the iconic dome are hollow and have a secret stairway.

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

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

A wondrous old library overlooking the nation's capital.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.