Oslo's Royal Palace was built in the early 1800s on a hillside overlooking the harbor. It's fairly small, as far as palaces go. Surprisingly, visitors are allowed to walk completely around the building and practically up to the front door. Tours are offered during the summer. Plan to arrive during the changing of the guards, a low-key but interesting tradition. Then explore Slottsparken, the expansive surrounding gardens--you can picnic on the king and queen's front lawn.