A marvel of Byzantine engineering under the streets of Istanbul.

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

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

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

Strange red rock formations that have been attributed to a higher power for hundreds of years.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

The design of this beautifully crafted building was inspired by Norwegian glaciers.

One man's exploration of the human form, including the bizarre and delightful "Man Attacked by Babies."

Home to three historic ships from the age of Vikings.

A whimsical bridge adorned with decorative dragons.

This one-time health resort was used by aristocrats around the world.

A miniature train-ride through Slovenia's largest cave system.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

One of two giant blue cockerel statues erected with an intentional double meaning.

A toweringly silly piece of modern art has been delighting locals since the 1980s.

A unique collection of diving equipment spanning antiquity to the present day.

This spiny beast guards an artist's village while vying for the title of largest lobster in the world.

Pensacola's UFO home has withstood many hurricanes—just as the experimental 1960s design intended.

This kitsch eatery is chock-a-block with bric-a-brac.

Wisconsin's most celebrated export gets the royal treatment on I-94.

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.