Olsborg Castle

Olsborg Castle was a fortified castle in Tanum Municipality, Bohuslan, Sweden, constructed in 1502-1504 by squire Nils Ravaldsson on a steep cliff that may have previously served as an early hill fort. It was largely destroyed on Christmas night 1504 when Otto Rud, commander of Bohus Fortress, attacked. The Swedes rebuilt the fortifications and administered northern Bohuslan from Olsborg between 1523 and 1525. Norwegian forces destroyed it again in December 1531, and later attempts at reconstruction by Eric XIV and Johan III failed. The ruins were excavated by archaeologist Wilhelm Berg in the early 20th century.