4x4 is a must, because of the condition of the road. We park the car at Stong, and hike over the bridge to the old viking farm, and went on to Gjain.

The road to Gjain is extremely rough. We had a lighter 4x4 vehicle and even we had a hard time. Probably one of the worst non-F roads we encountered. That being said, it's not illegal to try to take a 2 wheel drive vehicle (as I don't believe it's an F road). I did see one small car make it, but I have no idea how long it took them, or if they sustained any damage to their undercarriage. If you do this, I would just recommend letting 4x4s pass you (as drivers tend to get agitated when smaller cars attempt roads they shouldn't and hold up traffic). Also, look into your rental company and see how tough they will be if the car takes a beating.

There aren't any 4x4 signs for the road to Haifoss but there are for Gjain. In my opinion, a 4x4 would be a good idea for both drives. The road to haifoss has a ton of very large potholes and large rocks to clear. If its raining or really wet, you could find yourself stranded without 4 wheel drive. But, it is possible to make it with a regular car or SUV; just be very careful and go slow! For Gjain, the road is more loose dirt and gravel. When dry, which is was for us, its an easy drive and I felt like it could be done in a car more so than the drive to Haifoss. The difference maker would be if the road was really wet due to heavy rain. Without 4 wheel drive in that situation, you could find yourself stuck rather easily. My advice is get the 4 wheel drive, that way you can explore everything Iceland has to offer. Haifoss and Gjain were two of our favorite stops and well worth the extra money for the 4x4!!! Good luck!!!

There is only one road to Stöng and I would not recommend driving it in a regular car - although we did see one such vehicle when we were there I have no idea how they made it in one piece. The closest place to park and hike would be at Þjóðveldisbærinn Stöng (reconstruction of the excavated building at Stöng) but it is probably around a 10km hike to Stöng itself from there. We met a couple who had parked and walked (we gave them a lift back) as they only had a regular car - they were very glad they didn't try the drive! We were there in November 2016 and had a 4x4 (which we were very glad of!) If you do choose to drive in a regular car - as well as being exceedingly careful and driving very slowly - be aware that most rental insurance policies will not cover chassis damage (even if you have a zero excess) and many are invalidated if you drive a non-4wd on F-roads. Also driving off the established track is illegal in Iceland due to damage to the limited vegetation creating erosion problems. I would suggest hiring a 4wd for a short duration to make the trip. From Stöng it is a short hike (approx. 30 mins) to Gjáin (follow the markers). A longer walk (2-3hours each way) from Þjóðveldisbærinn Stöng will get you to Háifoss.