To the west of Strömstad lie the Koster Islands, noted for the beauty of its scenery. These are Sweden´s most westerly populated islands.The islands consist of North and South Koster. Around them lie the Koster archipelago with a large number of skerries and rocky isles. North Koster is a mere 4km2 consisting of both a beautiful and dramatic nature within a small area. Here you can find delightful beaches, heatherclad moors and brushwoods. On the westside, geological variations seldom seen are present, as are large cobblestone fields and clear traces from the last ice age. On North Koster, the lighthouses have arisen again. They are now, after 110 years, in use once again. The views from here are both enchanting and well worth a visit. The remains below are the ruins of lighthouse keeper´s residence. South Koster is the larger of the two islands, about 8km2. Here, bicycles can be rented and short excursions made. On South Koster there are large beaches such as Rörvik outside Ekenäs and the kilometer long sandy beach at Kilesand. The forests are larger and the tracks and roads more numerous. Remember, Sweden has right-hand traffic even when cycling on South Koster. Valfjäll, opposite the small wooden church is a beautiful and tranquil viewpoint. The stairway gives a helping hand on your way up and down. Here you can sit and gaze out over the Koster archipelago. There are many cosy restaurants on South Koster, each with varying menus. These are spread all over the island and you are never far from one. The sun shines often on Koster. Many times, when raining on the mainland, the sun still shines through on Koster. See also- http://en.wikipedia.org/wiki/Koster_Islands
https://www.vastsverige.com/en/stromstad/koster/