Danes attacked Birka, accompanied with the deposed king Anund, which caused great distress in the town.

Being in great difficulty they fled to a neighbouring city (ad civitatem, quæ iuxta erat, confugerunt) and began to promise and offer to their gods—But inasmuch as the city was not strong and there were few to offer resistance, they sent messengers to the Danes and asked for friendship and alliance. —
Hergeir, the faithful servant of the Lord, was angry with them and said, "They will lead away your wives and sons as captives, they will burn our city (urbs) and town (vicus)" and will destroy you with the sword (Chapter XIX)
As the neighbouring "city" is not mentioned in any other context than during the Danish attack as a place where people took refuge, it probably meant a nearby fortress.
Eventually Danes left, sparing Birka from destruction.
Danes attacked Birka, accompanied with the deposed king Anund, which caused great distress in the town.
Being in great difficulty they fled to a neighbouring city (ad civitatem, quæ iuxta erat, confugerunt) and began to promise and offer to their gods—But inasmuch as the city was not strong and there were few to offer resistance, they sent messengers to the Danes and asked for friendship and alliance. —Hergeir, the faithful servant of the Lord, was angry with them and said, "They will lead away your wives and sons as captives, they will burn our city (urbs) and town (vicus)" and will destroy you with the sword (Chapter XIX)
As the neighbouring "city" is not mentioned in any other context than during the Danish attack as a place where people took refuge, it probably meant a nearby fortress. Eventually Danes left, sparing Birka from destruction.
Birka