 Ullberg's most notable architectural design in Helsinki is Bensow House on Eteläesplaadi, completed for the Bensow trading company.While on the outside the seven-storey building is typically Functionalist in its expression, in the interior it has numerous features typical of Art Deco, such as the use of chrome, brick tiles and neon signs.After the Winter War with the Soviet Union, and following a short period in 1941 when Vyborg was occupied by the Soviet Union, Vyborg was handed back to Finland, Ullberg quickly drew up a plan for the reconstruction for his native town, but there was no opportunity to implement the plan because the entire city was annexed to the Soviet Union in 1944.