Tröllafoss, also known as the Troll Waterfall on the Grimsá River, is one of those Icelandic waterfalls that's almost forgotten in travel guides. However, given the beautiful surrounding nature, it can be the highlight of your day, especially since you'll have the area all to yourself. There's plenty to see.
If you want to visit Tröllafoss, you have two options.
The first option is to park your car near this intersection (GPS: 64.197489, -21.551507) and then follow this path until you're almost at Tröllafoss. If you choose this route, you'll only see part of Tröllafoss, so don't overlook option 2.
The second option is to park near the Hrafnhólar farm (GPS: 64.206926, -21.566052) and then walk upstream along the right bank. Here, you have two choices. The first is to walk along the riverbank. If you think you can't go any further, there is a rope you can use to climb about 5 meters. Even after that, you'll reach a point where the only way forward is to climb about 50 meters up a fairly steep hill. As a reward, you'll see a waterfall and many beautiful views of places few others see. However, you'll need to be an experienced hiker for this trail.