Altreu (medieval town abandoned)

Altreu, today a small hamlet belonging to the municipality of Selzach in canton Solothurn, occupies the ground of a medieval deserted town — a settlement that was once planned as a proper urban centre before being completely abandoned. The precise timing and causes of its decline remain incompletely documented, making the site of ongoing interest to settlement archaeologists. It is designated Swiss cultural heritage of national importance, class A. Perhaps unexpectedly, Altreu is best known today as the home of one of Switzerland's largest white stork colonies, established in the Aare floodplain — an unusual pairing of lost medieval history and active nature conservation.