Situated in the Northwestern Region of Iceland the F735 (Þjófadalavegur) is a difficult journey with breathtaking landscapes and rugged with a river. Only for 4x4 vehicles with significant fording capacity. No service or network.
The road runs west-east from Þjófadalir towards Hveravellir's thermal pool, a natural pool of hot water. It is a rough and challenging road. Should not be drive in anything else than a full size 4x4 with high clearance. It’s a bit steep in sections but not dramatic. Expect some deep holes/ridges in the track. Driving in a small passenger car is simply and plainly irresponsible and can be very dangerous. It’s a long and arduous drive through the rocky and oft barren interior of Iceland. It’s one of the famous F Roads of the country.
It’s only open during the summer months, usually between late June and early September. The drive combines strong stony slopes, broken sections, big rocks and muskeg. Expect to be alone, this track is not very busy even and very remote. In case of a breakdown, there is very little in the way of passing traffic or inhabitants around, and no cell phone service in parts. The road crosses incredible landscapes. It offers great views of lakes, mountains and glaciers. At Hveravellir you can find a parking lot and some facilities, including accommodation in mountain huts and camping and a cafe.
There is one river crossing of any significance. Shallow, but with a rocky river bottom. Crossing big rivers requires a bit of experience. Do not attempt to cross with one car, or during heavy rain. It can be treacherous if the water level rises due to lots of rain and warm weather. Only well equipped jeeps and larger vehicles are able to cross the rivers. Always check the river to ensure that it's not too deep. This road is amazing by day, but can be dangerous during the dark night. Rental car insurance does not cover damages from water, including any damage caused by crossing rivers.
Pic&more info: https://www.reykjavikcars.com/post/iceland-f-roads-opening