The F-roads (fjall which means mountain in Icelandic) are unpaved tracks that are not necessarily maintained. As soon as you leave the main road that goes around the island, you have a good chance of taking one. Some are easy to take, others more adventurous — river crossings, potholes, major ruts… There are no shops or gas stations along these roads either. If you rent a car, the 4×4 is imperative.