Little Pigeon River, Great Smoky Mountains National Park, Tennessee, United States

© GreenStock/Getty Image

Flowing through the Smokies. Little Pigeon River, Great Smoky Mountains National Park, United States

Blink and you miss it—until you hear it. The steady ripple, the splash of trout, the distant laughter of hikers. That's the Little Pigeon River, threading its way through the Great Smoky Mountains National Park in Tennessee, United States. Long before tourists tubed it and fly fishers praised it, this river was how people stayed afloat. The Cherokee tribe fished in it. Settlers built grist mills along it. Towns like Gatlinburg and Pigeon Forge grew up with it. Even the river's name is a nod to the past—the passenger pigeon, once common in the area, vanished by the early 1900s. The West, Middle and East prongs come together to form a system that cuts through the Smokies and flows into the Pigeon River. Trails like the Gatlinburg Trail run alongside the river, offering flat paths with water views and shady rest spots. Some hikes, like the Ramsey Cascades trail, follow the river deeper into the park and reward you with impressive waterfalls.

Another driver quietly charts its course across a very different landscape. The Bhadar River winds its way through the Saurashtra peninsula in western Gujarat. Starting near Jasdan, it flows southward before veering southwest and continuing westward, eventually meeting the Arabian Sea close to Porbandar. The river's basin spans a catchment area of approximately 7,094 square kilometres.