
15. Volga River (Russia) —
"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.

14. Li River (China) —
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. The river's breathtaking karst topography can be found between the Guangxi Province towns of Guilin and Yangshuo via boat tour, while traditional bamboo rafting can be done along the smaller and less crowded Yulong River (a tributary of the Li).

13. Loire (France) —
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.

12. Colorado River (United States, Mexico) —
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.

11. Caño Cristales (Colombia) —
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. 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.

10. Nile (Africa) —
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.

9. Rio Futaleufú (Argentina, Chile) —
Fed by Argentina's glacial lakes, the brilliant aquamarine waters of the Rio Futaleufú cross the Andes and cascade through southeastern Chile, where adrenalin junkies converge from November to March to tackle its heart-quickening rapids by raft or kayak.

8. Ganges (India, Bangladesh) —
The world's most populated river basin, "Mother Ganga" certainly isn't the world's cleanest or prettiest waterway, yet it remains India's most sacred river for Hindus. Witnessing pilgrims converge at the bathing and funeral ghats in the holy city of Varanasi may be one of the most profound travel experiences you'll ever have, but it's safer to swim much further upstream, closer to the Ganges' Himalayan source.

7. Kenai River (United States) —
Running 82 miles through southern Alaska's Kenai Peninsula, this meltwater river is the most popular sport fishing destination in the state. Each year there are two salmon runs, which also attract American brown bears (grizzlies) along with moose, black bears and multiple bird species.

6. Irrawaddy River (Myanmar) —
Several international companies now offer river cruises on Myanmar's mysterious Irrawaddy River with varying itineraries taking in ancient temples, remote villages, local trading centers and important Buddhist sites.

5. Danube and Rhine (Europe) —
The first European river cruises were on the Danube and the Rhine, and for good reason. Connected by a canal system, the two rivers gurgle through 12 countries between them, with baroque cathedrals, medieval towns and romantic castles a-plenty scattered along their banks.

4. Sepik River (Papua New Guinea, Indonesia) —
Referred to as the Amazon of the Asia-Pacific, Papua New Guinea's Sepik River is among the world's most diverse ecosystems. Winding through alpine heaths, dense tropical rainforests and mangrove swamps before emptying into North PNG's Bismarck Sea, this largely unchartered waterway reaches deep into a world that has remained virtually unchanged for centuries.

3. Río Cahabón (Guatemala) —
Never heard of it? Few had, until a few years back, when a section of the Rio Cahabón's densely forested pathway through central Guatemala was forged as a key stop on the Central American backpacker trail. Known as Semuc Champey, the series of spectacular steeped limestone pools bridging over the river are accessed via a hiking trail near the village of Lanquin.

2. Zambezi (Africa) —
Boasting superb wildlife watching, some of the best white-water rafting on the planet and the thundering beauty of Victoria Falls, the Zambezi is a showstopper. In the Middle Zambezi, which borders Zambia and Zimbabwe, you can bungee jump off Africa's largest waterfall, or tackle the grade IV rapids just below.

1. Amazon River (South America) —
Topping our list by an aquatic mile, the mighty Amazon River and its tributaries snake through the jungles of nine South American nations, providing a sanctuary for more than 400 indigenous Indian tribes and one in 10 of the known species on earth. For travelers, the possibilities are huge -- from wildlife spotting safaris to kayaking trips and gnarly jungle treks.



