Approximately 30km away from Sweden's capital Stockholm, in lake Mälaren, lies Björkö - a small island with great history. For Björkö is covered in Viking Age burials, some visible as grave mounds, others hidden beneath the soil. At the western border of the then-shoreline (which changed due to Scandinavia's post-glacial land rebounce) lies a former fortification surrounded by a rampart ("Borg"). North of this fortification is an area which, because of the dark colour of the soil, got the name "Svarta Jorden" - "the Black Earth". Beneath this area rests a Viking Age town. Probably the first town to be founded in Sweden: Birka.