Before Stockholm existed, there was Birka. In the eighth century, on a small island called Bjorko in Lake Malaren, a few kilometres west of the modern city, traders and craftsmen set up a market town, and for about two hundred years it was the most important trading centre in Sweden. Merchants brought furs, iron and slaves, and carried back silver, glass, silk and spices. Coins from Arabia and swords from the Rhineland have turned up in the graves, and a Christian missionary, Ansgar, came here around 830 to preach, with limited success. By the end of the tenth century the town had been abandoned, perhaps because the lake had become too shallow for ships as the land slowly rose after the ice age.
Across the water, on the neighbouring island of Adelso, lies Hovgarden, the royal estate that governed Birka. The huge mounds on the shore, the Kungshogarna, are burial places of local rulers, and the stone church, built in the twelfth century, stands next to a runestone. Together the two sites were inscribed on the World Heritage list in 1993 as an example of a Viking Age trading settlement and its administrative centre.
The island of Birka is reached by boat from Stockholm in summer, so a rider cannot simply roll up on a bike. The ride is to the lake itself, and to Adelso, which can be reached by a small, free road ferry from the island of Munso. Beyond that, you walk. The road out of Stockholm crosses the Drottningholm bridge and runs along quiet lanes among the farms and villages of the island of Ekero, with views over the water and the royal palace of Drottningholm on the way. The speed limits are firmly policed and traffic is light outside summer weekends.
Ekero has about eleven thousand people, with fuel and shops, and Stenhamra, a smaller place, has some services. The best seasons are late May to September, when the days are long and the light stays for hours. Pack insect repellent for the woods and a picnic, since cafes are few, and bring a jacket for the breeze on the water. The Birka museum, with its model of the Viking town, is worth a visit before you walk the ramparts.