The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

This chimerical bridge/tunnel appears to dead end right into the sea.

Old Danish castle immortalized in Shakespeare's Hamlet.

The shiny silver little brother to Copenhagen's Little Mermaid statue.

Just off the city’s central station hides a quaint lamp-lit alley into medieval Elsinore.

This pair of gilded girls atop an Art Deco building in Copenhagen were built to function as a weather indicator.

Discovered in a peat bog, these horned helms come from a thousand years before the Viking Age.

The only surviving piece of Copenhagen's 16th-century defensive wall.

What appears to be an ancient Roman temple is actually a Catholic church.

This Italian stadium makes liberal use of fascist statuary to evoke classical sporting arenas.

This rudder is one of the few remnants of a shipyard that once operated on the banks of the Potomac River.

Elevated freight railway turned wildly successful urban park.

One of the best examples of the modernist movement in Madrid.

Known as the Casa de las Siete Chimeneas, this haunted 16th-century manor has a dark, mysterious past.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

A vault of safe-deposit boxes in an old bank has been repurposed as a time capsule of Hispanic culture.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

This little sun pays homage to a massive gate that once stood at this location.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

Sometimes called the Banksy of Madrid, Muelle was a pioneer of street art in the Spanish city.

A small museum displays some of the artifacts discovered during a subway station renovation.

This girder was hit by a bomb during the Spanish Civil War, but nobody knew about it until 2016.