Travel 26 km (16 mi) from Grímstunga I to reach Iceland’s largest glacial river, Jökulsá á Fjöllum. 10 km west of the river is a road that will take you along the river to the canyons Jökulsárgljúfur, via the northern-most part of national park Vatnajökulsþjóðgarður. Europe’s most voluminous waterfall, Dettifoss, guarded by a majestic row of cliffs, is about 24 km / 15 mi away and is easier to see from road 864 (east side of the waterfall). Also other waterfalls are worth seeing; Selfoss is a little further up the river from Dettifoss, and Hafragilsfoss is a little further down the river. There are many marked hiking routes in this area, and you can also join organised guided tours that depart from village Reykjahlíð.