Touching this 18th-century Scottish philosopher’s toe allegedly conjures good fortune.

A six-ton wedding present for the King of the Scots.

A labyrinthine network of chambers with a storied past hides below Edinburgh's South Bridge.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

This striking observation tower shaped like a spinnaker sail is the newest icon in historic Portsmouth.

Hauled from the water's depths, Henry VIII's flagship is preserved in this capsule-shaped museum.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

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

Look closely and you’ll notice that the color changes a third of the way up the tower.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

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

The national park was once a plantation estate.

The most decorated dog of World War I is preserved in the Smithsonian.

There’s a hidden military meme engraved on the World War II Memorial.

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

Elevated freight railway turned wildly successful urban park.

Comprised of Spanish war cannons, this sculpture once graced the bow of a WWI warship.

One of the largest aviation events in the world brings half a million aircraft enthusiasts to Wisconsin each year.

A bronze plaque marks the site of the only show the "King of the Soul Singers" ever missed.

Software company Epic Systems has created one of the strangest and largest workplaces of all time.