Sigtuna's the place to see rune stones, named for the alphabetic letters, runes, used by the Vikings to encode their Norse language. Many of the stones are quite touching monuments erected by the living to honor their dead relatives. Our favorite inscription: "Anund had this stone erected in memory of himself." Bold, Anund.
Christianity found a bit more traction in Sigtuna than in Birka. There are many ruined, and many functional, churches here.