Gressholmen consists of three islands in the Oslo fjord, and it's a great spot for a slightly different Oslo outing. Especially on a sunny day, as they have just put in a big sand beach! Soak up the sun, take a dip, and check out an old lighthouse. Eat at Gressholmen Kro for a seafood meal. Just hop on a ferry from Aker Brygge (use your Ruter ticket), and enjoy!