Off the Beaten Path
Medeltidsmuseet (Medieval Museum Underground)
Underground Viking foundations, atmospheric reconstructed streets, and actual archaeological remains from medieval Stockholm, this museum earns its off-the-beaten-path status simply because most visitors to Gamla Stan walk right over it without knowing it exists. The different age ranges in your group will engage with it differently, which actually works: older kids and teens can dig into the history while younger ones absorb the atmosphere.