Oslo
Norway's capital is one of the cleanest in Europe — almost the entire municipal bus and ferry fleet is electric, the city centre is being rebuilt around pedestrians, and the new waterfront at Tjuvholmen and Bjørvika ties together the Opera House, the Munch museum and the Astrup Fearnley in a 20-minute walk. Most central hotels run Nordic Swan or Green Key certification, and the Holmenkollen ridge is a 25-minute T-bane ride for instant forest.
Highlights: Vigeland Sculpture Park · Opera House & Munch museum · Holmenkollen ski jump · Tjuvholmen waterfront