Ottoman-era houses lovingly preserved.

1513 Turkish world map, full of European state secrets and snarky commentary.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

Brass plaques embedded in pavement preserve the memories of those who lost their lives at the hands of Nazis during World War II.

Launched by Napoleon's soldiers more than 200 years ago, a cannonball remains embedded in the tower wall.

The inverted pyramid design of this station stands out amid Bratislava's urban landscape.

Hungarian self-built castle.

This historic spot was where America's involvement in the Vietnam War officially came to an end.

One of the oldest temples in Ho Chi Minh City, dedicated to a deified Chinese military leader.

Vintage furniture and art share space with all manner of collectibles at this quirky shop in Bangkok.

This crucial gathering spot along the "hippie trail" still displays old notes between traveling beatniks and backpackers.

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

The Brutalist building harbors an unusual inverted dome that swoops down over its central sacred room.

Mysterious man-made rock piles form an ancient cemetery on this rocky beach in Norway.

Stay overnight in the world's most sleekly designed rabbit hole, free of charge.