It's no wonder why we choose to build our cities near rivers — they give us water, natural borders and transportation. But they can also give us other things, strange things. Whether it's the boiling river in the Amazon that can cook animals or the unfathomably beautiful Caño Cristales that blooms with a rainbow of colors annually, we found 10 of the world's weirdest rivers.

The Boiling River Of The Amazon
1. The Boiling River Of The Amazon

The few Spanish conquistadors who survived treks into the Amazon jungle in search of gold returned with terrifying stories of man-eating snakes, debilitating diseases and a river so hot that it boils. For centuries, the boiling river tale was considered just legend, but not to geoscientist Andrés Ruzo. He went in search of the river, and eventually found it

Puerto Princesa Underground River — The Philippine Islands
2. Puerto Princesa Underground River — The Philippine Islands

The Philippine Islands are home to one of the world's more recently discovered natural wonders — a five-mile-long subterranean river that's accessed by a cave opening. While exploring the river in 2010, researchers discovered the river has a second floor, which means there are underground waterfalls within the cave. Insufficient oxygen levels make it impossible to explore this floor though.

Caño Cristales — Colombia
3. Caño Cristales — Colombia

Called the world's most beautiful river, the Cristales is extremely colorful, clean and devoid of fish. Between Colombia's wet and dry seasons, there is a brief period when algae and moss bloom in the river, providing its strikingly colorful appearance. Though, the part of the river where this occurs is extremely remote and hard to reach. 

Huang Ho River — China
4. Huang Ho River — China

Also known as China's Sorrow, this river has killed millions over the millennia with its devastating floods. In 1938, Chinese military leaders attempted to quell a rapid Japanese invasion by destroying dikes along the Yellow River, causing it to flood. It's estimated some 800,000 people — mostly Chinese citizens — drowned. It's been called history's largest act of environmental warfare.

The Amazon River
5. The Amazon River

You have to have some serious cojones to swim in the Amazon River. It's here you'll find the largest concentrated population of piranha (more than 30 species, some of which attack humans), electric eels, stingrays, and a host of other ghoulish fish that mean you harm. Oh yeah, anacondas live here too!

Rio Negro — South America
6. Rio Negro — South America

As the largest tributary of the Amazon River, the Rio Negro is also the world's largest blackwater river. Where Rio Negro meets the silty Amazon River, there is a visible division between the two rivers called the "Meeting of the Waters," which kind of looks like Guinness beer meeting Bailey's Irish Cream.

The Nile River — Northeastern Africa

Tim Muttoo via Flickr

7. The Nile River — Northeastern Africa

The Nile River is unique because it is generally considered one of the world's longest rivers, and it's one of only a few that flows south to north. On a more terrifying note, it's also home to the Nile crocodile, one of the most dangerous crocodiles on the planet. Each year, the croc kills hundreds of humans.

The Yarlung Tsangpo River — China

Boqiang Liao via Flickr

8. The Yarlung Tsangpo River — China

Sometimes called the "roof of the world" because of its average elevation of about 13,000 feet above sea level, the Yarlung Tsangpo River in Tibet is the highest-elevated major river in the world. Its conditions are extreme, and it attracts hundreds of whitewater kayakers annually. 

Danube River — Europe
9. Danube River — Europe

At 1,770 miles long, the Danube flows through seven European countries before spilling out into the Black Sea. Because it served as a natural boundary between European empire over the years (most famously as the northern border for the Roman Empire), the river's banks are lined with many medieval castles and fortresses. 

D River — Oregon
10. D River — Oregon

Capping off our list at a pathetic 4,330 feet is the pitifully tiny D River. In 1989, this sorry-ass excuse for a river was recognized by Guinness Book of World Records as the world's shortest river. But guess what? The famous record keepers eliminated that category from their books in 2006. So all Oregonians should be ashamed of this infinitesimal waterway.

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