Groups of prehistoric tombs that dot the mountains of northern Oman.

An imposing Omani fortress surrounded by date palm trees.

Nestled in the mountains of Portugal is a tiny village made almost entirely of schist.

A small Portuguese cottage formed between boulders in the countryside.

This gaping hole in the middle of a remote mountain lake looks like a portal to another dimension.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

Houses are tucked between, on, and underneath giant boulders.

The largest cemetery in Louisville is the final resting place of Col. Sanders and Muhammad Ali.

A theme park featuring a replica of Noah's Ark built to the measurements specified in the Bible.

Named the fifth most beautiful building in America in 1885, this former courthouse boasts the best view in the Village.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

A crumbling hospital from the 1850s on Roosevelt Island.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

A curious cave church carved into the face of a cliff.

Religious perseverance and cultural coexistence manifest in an architectural gem that multiple wars couldn't topple.

The interior of this Serbian royal family's mausoleum is covered with exquisite mosaics.

The bizarre rocks of Đavolja Varoš are the result of natural erosion.

A Serbian church lit by chandeliers made of weapons.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

This sign marks the entrance to a tiny proto-state within the small country of Moldova.

The largest wine cellar in the world is a 150-mile network of underground caves near the capital of Moldova.