This 13th century Gothic brick castle is the largest in the world by surface area.

This fairytale inspired, warped building houses restaurants, shops, and a radio station.

This Communist-era residential block is one of the longest residential building in Europe.

Memorial to the lost dead of Gdansk, whose resting places were destroyed during World War II.

A floundering Polish shipyard was once the soul of the Solidarity movement that capsized communism.

Modern art commemorates one of the first military actions of World War II.

A mysterious emblem tucked in an small alleyway is actually the coat of arms of a heroic medieval family.

This antique thermometer honors the creator of the first universal temperature scale.

This gateway to subterranean Hanover plays jazz, pop and rock to surprised passersby.

How did a lighthouse wind up in the middle of this landlocked German city?

The last Tsar of Russia constructed this private church just so he could attend services when visiting his wife's hometown.

Crop circles inspired this whimsical garden in Germany.

Taking the subway here means doing so over a bridge located in the middle of an estuary.

Climb a set of vertiginous stone steps to the top of this impressive ancient edifice.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

Ancient serpentine sacrifice holder that has stood the test of time.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

A meow-velous tribute to a beloved street cat, made famous on the internet.

This amazing example of Valencian Art Nouveau looks more like a cathedral than a public market.

Walk into an underground archeological dig, the site of the Roman Forum that was once the center of Valencia.

Vibrant street art created with mixed media.

This abandoned viewing platform has become a monument to unnecessary government spending.