This colorful city, situated on the Nidelva River (or the Nid, for short), is Norway’s third largest — and one of its most historic. Viking King Olav Tryggvason established Trondheim in 997 and was later canonized as Norway's patron saint. The Nidaros Cathedral built atop his gravesite is a must-see attraction, while the city itself is easily walkable and less than 15 minutes by foot from the cruise terminal.