Fittingly, America's museum of architecture is itself a magnificently designed old building.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

Inside this McDonald's you can dine on your Big Mac and fries next to a 2,500-year-old Roman wall.

These tall, red sandstone pinnacles outside Moab are often forgotten amid their more famous neighbors.

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

Few things look more out of place than the electric blue ponds in the reddish-brown desert of Utah.

The fifth-longest natural arch in the world, and the longest outside China.

A labyrinth hides in plain sight at each of the city's 270 Tube stations.

Originally meant to hold a statue of King William IV, this support sat empty for years. Today, it hosts a rotating cast of public artwork.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

A mysterious shape catches the eye in this 16th-century painting.

The television series' iconic giant foot was borrowed from this classical painting.

A gruesome and mysterious ancient sculpture of a pagan deity from the Roman occupation of Celtic Britain.

This intriguing Bronze Age artifact spent centuries hidden within a Welsh faerie hill.

These mysterious Viking chess pieces spent centuries hidden on a remote Scottish island.

The "lost friend” is the most famous of the six moai statues that were removed from Easter Island.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

Less a museum than a bizarre fantasy world created by artists and engineers.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

The unluckiest U-boat in the entire German fleet is now on display in a Chicago museum.

This bronze sculpture on a former squash court marks the secret origins of the Atomic Age.

An actual 1957 Cadillac De Ville, encased in 15 cubic yards of concrete.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

Hidden on the seventh floor of a historic building, this Cajun spot features wall-to-wall bottles of hot sauce.