Birka, Archaeological site in Ekerö Municipality, Sweden

Birka is an archaeological site on the island of Björkö in Lake Mälaren, where the remains of a medieval trading settlement lie scattered. The ground holds numerous burial grounds and building foundations that show how people lived and worked here.

Birka was founded around AD 750 as a trading port by a king or merchants seeking to control trade, and it flourished for more than 200 years. It was abandoned around AD 975, roughly when Sigtuna was founded as a Christian town some 35 km to the northeast. The reasons for its decline are disputed, with theories including the rise of Sigtuna, the post-glacial rebound isolating its harbour, and Gotland's better position for eastern trade.

Excavations reveal how people from distant lands came here to trade their goods. Arabic silver coins, Eastern European beads, and Asian textiles show that this place was known far beyond local borders.

The site is reachable by boat, with a journey of about two hours from central Stockholm. Guided tours are available during the warmer months and help visitors understand the ruins properly.

The stone cross on Borgberget hill was raised in 1834 as a memorial to Ansgar's mission, not to mark a Christian gathering. Its ringed shape imitates a Celtic cross, which is misleading: it recalls missionaries from the British Isles, Ansgar's rivals in converting the North.