Looks unreal in the winter. Semi moderate walk around the rim.
Although it's physically challenging to climb the hill to reach the crater because the slope is steep, ash is deep and the wind is gusty, once at the top, the view is fantastic. Get your 4x4, don't go in an econo or you will get nowhere. And be careful, this is not for the faint of heart. Plus Hekla is an active volcano that has last erupted in the year 2000 and is the most active volcano in Iceland so think twice before going.