Jökulsárgljúfur National Park encompasses Iceland's most celebrated canyon of the same name, which channels Iceland's second-longest river, the Jökulsá á Fjöllum. The river's opaque, gray water carries sediments from Iceland's largest glacier, Vatnajökull. A comparison to America's Grand Canyon and the Colorado River is tempting, but Jökulsárgljúfur does not register on such an instantly overwhelming scale. Rather, its treasures -- including an extraordinary range of basalt formations, waterfalls, and plant life -- unfold at each turn.
The ideal way to experience Jökulsárgljúfur is by taking a 2-day hike from bottom to top, but day hikes suffice for most. The busiest season is mid-June to mid-August, so if you crave solitude -- and wish to avoid rowdy revelers at campsites -- aim for late May to early June or late August through September.
Jökulsárgljúfur and Skaftafell parks are in the process of merging to form Vatnajökull National Park, the largest in Europe. New parkland will be added -- including the entirety of Vatnajökull Glacier -- to make the new park contiguous.