The Ansgars Cross or Ansgar monument (Swedish: Ansgarskorset) was raised 1834 at the 1000th year anniversary of the missionary Ansgars arrival to Birka on the island Bjorko (Swedish: Björkö) in Lake Malaren (Swedish: Mälaren). Birka (along with HovgÃÂ¥rden) has been a UNESCO World Heritage Site since 1993. Sweden.