The two-storey Sovelius house on the north side of the square was built in the 1780s. It is the oldest preserved dwelling house in Raahe. The house of the Sovelius’ shipowner family tells not only of the life of a middle-class family in the 18th and 19th centuries, but also of the architectural history. The early boarding of the house, vertical boarding finished with profiled covering laths, dates even from the 1790s. In addition to the covering lath boarding, there are several other architectural novelties visible from the latter part of the 18th century in the Sovelius house: the house is built on a stone base, it has preserved its carolinian floor plan and traces of red ochre painting have been found in the outside walls, both in the logs and the boarding.

Today, the house is in Raahe museum’s use. The upper floor has been restored to its appearance of the 1890s, and a shipowner-merchant interior museum is there in preparation. The museum office is located downstairs and changing exhibitions are also held there. The lower floor has been restored in the spirit of Art Nouveau to the appearance of the beginning of the 20th century. The Sovelius house was painted in connection with the restorations chrome oxide green, as in the 1890s. In its time, the Sovelius house was called “Gröna slottet” (the green castle).