This remote island nature reserve is home to extensive bird life including thousands of guillemots and razorbills, as well as the maculinea arion (large blue butterfly). For nature-lovers, it's well worth the travel time needed to get there. You can visit the island as a day trip (with 3½ hours ashore) or stay overnight.
From Klintehamn harbour, catch the passenger-only Klintehamn-Stora Karlsö Farje to the nature reserve one to three times daily from May to early September (adult/six to 15 years return 345/155kr, 30 minutes).