As a big history buff, I really enjoyed the day trip to Birka (Bjorko). You must go as part of a package deal. There's not a lot on the island - the small museum takes, at most, 30 minutes. The Viking town ruins are not conspicuous, except for the ramparts around the hillfort. However, it's a lovely little island and if you've done a bit of background reading and have a good imagination, it's very evocative and I could have easily spent 2-3 hours longer than we had on the island. There's a small restaurant on the island that opens to meet day trippers for lunch. I highly recommend also making a reservation to have a late lunch/early dinner on the trip back to Stockholm. Make sure you take one of the guided tours that begin at the museum (once daily in English).
Thank you for writing a review! We´re so happy that you enjoyed your day trip to Birka! Take care!