Haifoss (more accurately Háifoss; I think it's pronounced "HAU-i-foss") is said to be the second tallest waterfall in Iceland at 122m tall. What made this waterfall stand out was that it was also accompanied by a similar waterfall called Granni (the Neighbor) in an adjacent gorge. It seemed like we got lucky with the timing on our visit because not only did we see both waterfalls at their full flow, but the sun's position was almost perfect as it yielded bright quarter-arcing rainbows within the mist of the main falls. Add to that the hauntingly beautiful yet desolate landscape of the Icelandic Highlands and we still think about this place whenever we reminisce about our 2007 trip to the country.
In order to reach this waterfall, we had to take a detour on a rough road (it seemed like it required a high clearance vehicle though we saw a 2wd vehicle make it) to its car park (see directions below). From the car park, it was a short walk (maybe 20-25 minutes round trip) on a gently downhill path to get to the best views of both Haifoss and Granni.