Longos Mansion is one of the most wonderful buildings in the city center, in Agia Sofia square and across from the church of the same name. It was built in 1926, by the Italian architect Leonardo Gennari, who designed several other important buildings in Thessaloniki at that time and retains its glory to this day, especially after the recent restoration. It is better known as the "Red House" because of the characteristic red color of the brickwork.
The building was built by order of the Naoussa businessman Grigoris Galakis Longou and has four levels, ie ground floor and three floors, the tallest of which was later added to the original plan. The appearance of the building is characterized by arches on all the windows and balcony doors, as well as special decorative elements. It belongs to the current of eclecticism, with neo-Byzantine, Gothic, and Art Nouveau influences. Inside it has several decorations with wooden frames, plaster and painted ceilings, carved metal railings, and elaborate chandeliers. It was declared a protected site in 1983.