Building established in 1773 for military purposes. NGO since 1880.
A good place to introduce the post-glacial uplift.
Maximum relative sea level at 221 masl today (a bit above the level of Sognsvann).
Uplift since the Viking age: ca 3,8 meter.
Normalhøydepunktet was moved to Mandal in 1954 (where the elevation system “normalnull 1954” is based). Normalnull is the mean sea level.