I am going to Iceland for the second time in December. I went last October and fell in love and already did some of the main tourist highlights (Golden Circle, the southern coast, caving, snorkeling, Blue Lagoon, and horse back riding). I am coming back mostly to see the Northern Lights, but I will be there for 8 days. Are there any other great suggestions to do and would it be unrealistic to rent a car? I am completely open to all ideas, even fun bars to go to in Reykjavik.