Reykjavík

Reykjavik needs 3 days: the center and Hallgrímskirkja church on one, and Golden Circle or Blue Lagoon trips for the rest. June-August brings the best weather and near-endless days thanks to Nordic summer light. It's expensive, among the world's priciest capitals. It's the world's northernmost capital among sovereign countries, and serves as a base for exploring a country with more geothermal energy per capita than any other, as well as being one of the best spots on the planet to see the Northern Lights in winter.