If only the towering walls of Tønsberg Castle could talk! But as they can't, inquire if tours are available to hear a couple of its tales instead.
You'll have no end of sightseeing choices when visiting Tonsberg. Tønsberg Castle is a great place to kick off here, but there are plenty of other interesting attractions to enjoy. Tonsberg Cathedral, Slottsfjellsmuseet, and Hellastranda are not far from the fortified complex and and will cap off your day nicely.