Dettifoss definitely blew us away with its sheer size and power. Perhaps a waterfall so wild and fierce was befitting of an area that just screamed natural and raw as it flowed on the glacial river Jökulsá á Fjöllum ("YUK-ul-sou ow FYUHT-lum") meandering through Iceland's version of the Grand Canyon - Jökulsárgljúfur ("YUK-ul-sour-glyoo-fur").
And to back up our adjectives, we've learned that this falls has a flow of about 500 cubic meters per second at high flow, with dimensions of 44m tall and 100m wide. Add it all up and we witnessed a monster that is quite possibly Europe's largest and most powerful waterfall (let alone Iceland's biggest). The milky color of the waterfall is due to the fact that the massive river is fed by the sediment-rich meltwaters of the vast Vatnajökull glacier.
Given the wild nature of the falls (it's unregulated and protected by being part of the Jökulsárgljúfur National Park or Jökulsárgljúfur þjóðgarður), its rate of erosion (and therefore its propensity to move further upstream) is very high. We definitely didn't want to get too close to the edge and fall into the raging and frigidly cold river (there are no guard rails)!
We managed to experience this waterfall from both sides of the river - each quite different in their own way.
On the west bank, we got some dramatic close-up views of the falls while photographing it dwarfing people on either side of the river! In the afternoon on a sunny day, we also managed to see rainbows in the wafting mist rising from the base of this thundering waterfall. It seemed like this was the place to be at this time of day, and the photo you see above came from the west bank in the late afternoon under sunny skies.
But with the fickle weather, we also happened to be on this side during frigidly cold and rainy weather where it was very difficult to see anything. That might be something to consider if the weather's foul and you're flexible enough to defer a visit here until the weather improves.
There was also a trail that took us a short distance further upstream to get distant views of Selfoss.
On the east bank, we got more angled and profile views of Dettifoss near its brink. The lookout area on this side was much longer so it was also possible to scramble a little further downstream to get better views of the entire falls including its misty and inaccessible base.
Further upstream from the brink of the falls, there was a fairly straightforward walking path that went to the brink of the horseshoe-shaped Selfoss (see that page for more details).
The east bank was the more popular side of the river as tour buses routinely stop here and unload their passengers (probably since the access road here was more tame compared to the west bank access). Thus, it was much more busier here and certainly not as peaceful and quiet as the west bank.
Directions: To reach the west bank, drive east along the Ring Road from Reykjalið on the eastern shores of Mývatn (in case you didn't know, that's translated as "Midge Lake", yikes!) for about 18km. Then, turn left onto the rough and rugged signposted 4wd route 862 (though we've seen some 2wd risk damage to their rental car to get here). Continue about 20km from the Ring Road then turn right at the signposted turnoff for Dettifoss. Ignoring another turnoff for Hafragilsfoss at 1.8km from the turnoff, continue another 1.3km to the car park. From the car park, it's about 20-30 minutes walk (I think) to the falls overlook area.
The east bank is the more touristy side though it too requires driving on a bumpy unsealed 2wd road on Route 864 (though this route is not nearly as rough as 862; even tour bases take it). From Reykjalið, head east on the Ring Road for about 37km (or 19km beyond the turnoff for Route 862). Just beyond the bridge over Jökulsá á Fjöllum, turn left onto Route 864 and follow this wide and relatively tame unsealed road for about 31km. There's a signposted turnoff to the left leading the last kilometer to the car park. From there, it's a short 10-15 minute descent to the brink of Dettifoss.
Finally, we must note that the river can't be crossed in the immediate area. Your only opportunities to cross the river are where the Ring Road bridges the river to the south and where Route 85 bridges the river near Ásbyrgí to the north.