They irrigate our farms, they're an important means of transport, they're a source of eco-friendly power. Rivers are the life-giving arteries of our planet.
For travelers they can be a whole lot of fun too.
From exotic wildlife hubs to whitewater rafting hotspots and the most scenic stretches for cruising, we've highlighted 15 rivers worth basing your next trip around.
We've made our ranking on five travel criteria.
Scenic beauty -- the physical beauty of the river; waterfalls, color, drama of the landscape.
Nature and wildlife -- diversity and prevalence of flora and fauna.
Culture -- depth, diversity and accessibility of local culture; tribal/medieval villages etc.
Adventure -- thrill factor of the river's topography and location
Activity options -- rafting, wildlife watching, hiking, biking etc.
We've debated among ourselves, researched expert views and polled our colleagues and fellow travelers around the world, to score each river for these qualities. We think we've put together a pretty great bucket list for inland water babies.
15. Volga River (Russia)
Scenic beauty: 3 | Nature and wildlife: 2 | Culture: 3 | Adventure: 2 | Activity options: 2
According to an old Russian proverb, to know Russia is to know the Volga.
Winding through the nation's heartland, "Mother Volga" houses 11 of Russia's 20 largest cities on its banks, which explains its popularity among the cruise set.
Most tour boats ply a section of the Volga just north of Moscow before traveling on to St. Petersburg via a series of interconnected waterways, taking in major cities alongside quaint riverside towns sprinkled with historic Kremlins and brightly colored onion-domed churches.
Frozen for three months of the year, the Volga is best visited during the height of summer.
14. Li River (China)
Scenic beauty: 5 | Nature and wildlife: 2 | Culture: 2 | Adventure: 1 | Activity options: 3
China might be known for the Yangtze, but it's difficult not to fall under the spell of the Li (Lijiang) River, one of its tributaries.
It's possible to take in the river's breathtaking karst topography -- likened to the limestone cliffs of Vietnam's Ha Long Bay -- between the Guangxi Province towns of Guilin and Yangshuo via boat tour, while others prefer to opt for a more traditional bamboo rafting trip along the smaller and less crowded Yulong River (a tributary of the Li), both of which can be organized from Guilin.
13. Loire (France)
Scenic beauty: 4 | Nature and wildlife: 2 | Culture: 3 | Adventure: 1 | Activity options: 2
As European road trips go, it's hard to beat a scenic drive along France's longest river.
Dotted with grand chateaus steeped in history, sprawling, manicured gardens and undulating green hills stretching to the horizon, the Loire also lends nicely to cruising. But with no pesky border crossings to account for, most travelers prefer to navigate its length on four wheels, or, thanks to a proliferation of cycle ways, by bike.
Though given the number of vineyards en route, it can be slow going.
12. Colorado River (United States, Mexico)
Scenic beauty: 4 | Nature and wildlife: 2 | Culture: 2 | Adventure: 2 | Activity options: 4
The principal waterway of the southwestern United States, the Colorado River has something for every type of traveler.
Flowing down form the Rocky Mountains, dammed areas including Lake Powell in Arizona, Lake Mead in Nevada and Lake Havasu on the border of California and Arizona are popular house boating, weekend recreation and spring break party destinations respectively, while the section that cuts through the Grand Canyon attracts whitewater rafting enthusiasts, kayakers and tubing fans.
Further south, the river runs through a series of threatened wildlife refuges before drying up in the Mexican desert.
11. Caño Cristales (Colombia)
Scenic beauty: 5 | Nature and wildlife: 3 | Culture: 2 | Adventure: 4 | Activity options: 1
Known as "the river that ran away from paradise," the Caño Cristales in central Colombia is often considered the most beautiful river in the world.
For most of the year, this Orinoco River tributary is virtually indistinguishable from any other.
But during the summer months, when the heat helps resident algae colonies to grow and multiply, the river explodes in a multi-hued array of colors worthy of a thousand photographs.
Off-limits to tourists for many years due to militant activity in the area, the river hub town of La Macarena is now welcoming travelers.
10. Nile (Africa)
Scenic beauty: 4 | Nature and wildlife: 3 | Culture: 4 | Adventure: 3 | Activity options: 2
Recent events may have forced most travelers to put a trip to Egypt on the backburner, but fortunately the world's longest river -- which shares its resources with 10 other countries -- isn't going anywhere.
From the tomb-laden Valley of the Kings to the monumental Temple of Luxor, the riverbanks of the Nile house almost all of Ancient Egypt's historical sites.