Here's a biggest/furthest claim for Harstad: this formidable WWII weapon is the world's largest land-based big gun, with a calibre of more than 40cm and a recoil force of 635 tonnes. Because it's in a military area, you're obliged to take a guided tour of the site and to have your own vehicle. Check ahead for times at the tourist office. The bunker also contains a collection of artillery, military equipment and instruments used by Nazi coastal batteries during WWII.