One of Iceland's most active volcanoes, Hekla stands at 1491m, and has erupted 20 times since 874, most recently in the year 2000. In a 4x4, it's possible to drive right up to the volcano's base and do a moderate hike (three to four hours, around 7km) to the rim, where on clear days there are marvellous South Iceland views. However, be aware that Hekla is due to erupt any day – adding plenty of thrill factor, but potential fatalities.
Some tour companies currently don't take guests onto the volcano due to the imminent danger. Most people choose to enjoy the volcano from afar. That said, the hiking route to the rim remains open. The Hekla Centre has up-to-date information on the volcano, and from there it's around 16km to the Hekla trailhead and parking area, via the F255 road (4x4s only) off Rte 26.