This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

This 170-year-old Swiss guesthouse built into the side of a mountain is best accessed by a cable car.

A striking 12th-century-style castle built on the edge of a cliff.

The medieval center of the Islamic world was also once the seat of Saladin's sultanate.

Slum Settlement Filled With Mountains of Garbage.

In Egypt's expanding metro area, many of the neighbors are dead.

A preserved oasis with traditional Andalusian-style architecture and beautiful views of the Nile.

An ancient instrument used to measure the waters of the Nile so Egyptian farmers would know whether to expect famine or flood.

Mortarless walls that stretch for miles are a lovely solution for creating grazing land in the harsh terrain of the Aran Islands.

The modern birthplace of Irish freedom.

The house where the writer spent his formative years.

One of the oldest family businesses in Reykjavík serves lamb-based hot dogs.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

A once-fairy tale mansion now stands in a state of disrepair.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

The 700-year-old fortress was the site of Count Orlok's castle in "Nosferatu."

The slender brass strip in Prague's Old Town Square was used to tell time from 1652 to 1918.

This doorless 20th-century elevator doesn't stop or slow down.

This artificial cave looks like something out of a fairytale.

Macabre astrological automaton clock dating to the late 1400s.

Legend says this sacred tree was a gift from goddess Athena.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

This church is named for one of the most dramatic tales in the early Christian church.