The reason these were built on Hovden was because the German Navy could protect its own ships and convoys around Stad against allied aircraft attacks. A 100 meter long tunnel runs through Hovden and from the end of this there is a cable car which was installed to go down to Little Hovden where a small tunnel was also built. The main tunnel has a side tunnel that is almost the same length and ends in a shaft. This tunnel facility is open, and an information board has been set up along a path up to Hovden.
On the way up to Hovden, a camp with Russian prisoners of war was set up by the Germans, to work on Hovden. In the hard work, many Russians lost their lives, and they were provisionally buried near the camp. Just after the war, they were moved to the graveyard at the Ervik chapel, and the crusade with the text "Here rest 21 Russians", signs are still to be seen at the Ervik chapel. The graves were later moved to their own grave site for Russian prisoners of war in Norway. There are no safe numbers for how many Russians there were in Ervik, but it could be between 100 and 120. Nor the numbers of those who lost their lives are sure, but they can be between 21 and 32 prisoners who died in Ervik.