Next to Hekla is this Red volcanic crater. The drive there goes through a lava field and then you get to a parking lot. From here you can hike up to the crater or simply just drone from the car. It's about 1h hike round trip in lava so wear good shoes as it can be very sharp. On the way in you will also see warning signs that Hekla is an active volcano and can have an eruption. If she starts you need to get out of the area quick.