Gustaf Dalén, Reinforced concrete lighthouse in Sottunga, Finland.
Gustaf Dalén lighthouse is a reinforced concrete structure on the eastern coast of Sottunga island, marking the entrance to the Åland archipelago waters. The structure was built using a distinctive caisson foundation method, where the base was constructed directly on the seabed with watertight chambers.
Built in 1947, this structure was part of Finland's maritime infrastructure reconstruction following World War II. Its construction reflects the technological advances in Baltic lighthouse engineering during that rebuilding period.
The lighthouse carries the name of Nobel Prize winner Gustaf Dalén, whose inventions transformed automated maritime lighting systems worldwide. Visitors can still see traces of this innovative engineering in how the structure was built.
Modern LED lights have replaced the original gas system, operating year-round to guide vessels through the narrow passages between islands. The best time to visit is during clear weather when the structure is clearly visible from the water or nearby viewpoints.
The foundation was placed directly on the seabed using watertight chambers, a method that was innovative for its time. This caisson construction technique was necessary to create a stable base on the unstable seafloor.
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