A 1,215-foot tunnel transports pedestrians beneath the River Thames.

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

World's largest cave was only discovered in 1991, and now offers tours to the public.

This network of tunnels housed an entire village for years, and even had a hall for screening movies.

An unusual manor of stunning beauty, born out of a crippling disease.

An extravagant monument to an extravagantly unpopular Emperor.

Vietnam's feral abandoned water park offers access to a post-apocalyptic funscape, now with fewer crocodiles.

Giant pagoda houses the car that drove Thích Quảng Đức to his death by self-immolation.

This spectacular bridge supported by two gigantic hands looks like something out of a fantasy universe.

This cavern was used as a hidden hospital and safe house during the Vietnam War.

The notorious "Hanoi Hilton" where Vietnamese colonial subjects and later American POWs, including John McCain, were imprisoned.

Ho Chi Minh's perfectly preserved body has been on display here since 1975.

Monument to a brutal, ineffectual US bombing campaign and a sobering reminder of the human cost of the Vietnam War.

Home of the unusual art of water puppetry, one of Vietnam's oldest curiosities.

Twice a day a speeding train passes only inches from the homes of this residential neighborhood.

Life-sized painted illusions let pedestrians blend in with the street art.

This ancient Irish tower could easily have stood in for Rapunzel's prison.

Catholics make up 84% of Ireland's population but this Dublin museum remembers the small but important Jewish community.

An ancient neolithic tomb that only sees the sun twice a year.

While only two of the ancient buildings at this site are actually churches this was one of the earliest Irish pilgrimage sites ever.

A remarkably intact castle that once was the largest in Ireland.

A steam trawler with a whiskey-soaked history driven ashore in 1960 resides rusty but still standing on the shoreline.

A sacred well steeped in Pagan roots on the West Coast of Ireland.

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.