Reykjavik
We only did a quick stop in Iceland and would have loved to stay longer. In general, most items are much more expensive in Iceland, so prepare yourself for that
Harpa Concert Hall is a fascinating glass concert hall. Its open when there is not a show on, and there is a cafe inside.
Hallgrimskirkja is the famous church on the hill and worth walking past or heading up to the top.
Blue Lagoon This is worth the stop, and there is a bus that will take you straight to the airport (the Lagoon has adequate lockers for luggage), so a good way to see this is before an evening flight.
We stayed on the Old West Side, which turned out to be a bit further of a walk than we anticipated into city center. We’d suggest staying more central; the city is not that big.