My wife and I going to Iceland in June and we'll have about 4-5 days to travel before I have to give a talk in Reykjavik. I'd appreciate any tips anyone has about sights to see and things to do. I'd especially appreciate any tips about underrated activities that we wouldn't find in a guidebook or overrated activities that a guidebook typically would recommend but that we should consider skipping. We plan to rent a car. Thanks!