The usual tour items above are all great. We went for a short trip a few years ago and loved driving around with our great tour guide.

Beware of the Viking Feast restaurant! It was great atmosphere and a great show, BUT the Black Death shots don't do their name justice. Avoid the petrified shark meat too. Sticking to beer and edible food, you'll have a nice time, I'll bet. I was never given that advice and I paid for it on the flight home the next day.

Oh yeah! While in the city, you HAVE to get up the first thing in the morning and hit one of the local public pools. The Blue Lagoon is great and all, but there's geothermally heated pools right in the city. We also went in March and it was a great way to start the day. You mostly see locals at the pool which adds a new dimension to the experience.