Used as an example in one of the first dictionary entries for "museum" in 1706.

This Norman castle was once the site of a Victorian-era prison, and now exists as a luxury hotel.

A unique seaside cave where Aleister Crowley faked his own death.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This tile-work piece featuring a chicken riding in carriage is both a remarkable artistic creation and a social commentary of politics and culture in 17th-century Portugal.

This once-forgotten oasis in the middle of Lisbon was first created over a century ago quite by accident.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

The world's oldest bookshop still in operation.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

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.

This statue of one of baseball’s greatest pitchers looks like something out of a sci-fi horror movie.

The oldest continuously operating fish market in the United States.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

A spectacular tribute to statesman and philanthropist Andrew Mellon.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Washington's iconic carousel has a nice piece of Civil Rights history.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

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

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.