The Great Barrier Reef is the largest reef system on Earth, with more than 3,000 separate reefs and coral cays. It is also one of the most complex natural ecosystems.
In Western Sahara, an unusual river vanishes in a sand field before it reaches the sea. In the process, it provides water for the largest city in the country.
Grand Canyon National Park spans 277 river miles and often stretches 10 miles wide. But the true wonder arises from its depth...or height, depending on where you stand.
Astronauts are taught to concentrate on the shapes of coastlines for a visual cue about where they are when circling the planet. The nose of Cape Karmel and the bay that protects Haifa are shapes that stand out.
An astronaut aboard the International Space Station shot this photograph looking north into the snow-covered landscape of Canada’s Coast Mountains, the Canadian Rockies, and Vancouver Island.
Crews aboard the International Space Station often look for signs of human activity along the coastlines of the Persian Gulf, where a growing Middle Eastern population has been moving.