The ceiling of Prohodna Cave in northern Bulgaria affords a peek at the sky via two deity-sized-eye-shaped holes.

The site of many battles and tragedies, including the 40 maidens who leapt into the sea.

Massive, unfinished broadcasting station stands as a monument to the fall of communism.

The atmospheric road was never meant to be so creepy.

Romania's triumphal arch looks out over Bucharest.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

This massive monument has been telling the time for 150 years—at a slight angle.

The last Victorian market in Belfast.

The world's largest frame offers spectacular views of the city's past and present.

Over the dunes of the Empty Quarter, the mysterious music of the desert.

Whitewashed mosque contains the world's largest carpet.

This living legend of maritime history is enjoying a second life.

A preposterously luxurious hotel with gold-plated iPads, Rolls Royce chauffeurs, and a staff that trains by watching "Downton Abbey."

This artificial archipelago was supposed to resemble a map of the world.

This indoor ski resort has a mountain contained inside a mall.

Why a column on the entrance is inscribed with a verse from the Quran is one of Sicily's many mysteries.

Every inch of this chapel is covered in craftsmanship from across the world.

This mosaic-lined medieval church was built by the world's first admiral and still holds mass in ancient Greek.

A medieval wash house where people washed clothes in a river allegedly formed by the tears of a mourning nymph.

"Stairs of the Turks", a chalky white cliff eroded conveniently into stairs, allowing for easy pillaging.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

A magnificent collection of imperial armor and weaponry.