Mývatn is not a very big lake. You could easily drive around its perimeter in about 45 minutes and so it was a little surprising when our loop turned into an all-day adventure. But we weren't about to speed past sights as amazing as the Höfði Nature Park or the psedudocraters of Skútustaðir.
Driving around Iceland with a guidebook and a map can be rewarding, but even the most astute tourist won't find everything on their own. To reach certain places, you'll have to enlist the help of experts. That's what we did, in order to explore a secret lava cave and an amazing hot spring.