The best hiking routes in Kosteröarnas naturreservat

Kosteröarnas naturreservat covers the Koster Islands, where the landscape is split between the rocky, barren shores of North Koster and the more sheltered, wooded paths of South Koster. Walking here means navigating a mix of bare, wind-scoured gneiss rock, shingle fields, and small patches of coastal forest. The terrain does not offer high peaks or deep valleys, but rather a low-lying, undulating profile of exposed stone ridges and sandy depressions. Underfoot, you will transition from smooth, open rock surfaces to sandy tracks and wooden boardwalks that cross the wet, marshy hollows.

The stark contrast in vegetation is a direct result of the islands' exposure to the sea. On the western edges, the plants are stunted and hug the ground, while the eastern sides support small pine woods and deciduous groves. You will notice dark, narrow clefts in the bedrock, known as diabase dykes, which have eroded faster than the surrounding gneiss to form natural pathways and sheltered microclimates where richer soils have accumulated.

While the main tracks near the ferry piers are wide and easy to follow, the trails quickly narrow into rugged paths over uneven stone. In the summer months, particularly July, the harbor areas and central paths are busy with visitors, but the outer rocky headlands and the southern shingle fields remain quieter. There are no bridges between the two main islands, so choosing where to walk determines whether you will spend the day on the smaller, more rugged northern island or the larger, more varied southern island.