Many buildings from the 1890-1920 era have these interesting shapes at the rear or side of the building. The tall shape was a door, to a roof, a balcony or stairs. However, there appears to be at least two windows below and one on each side of the door. Remember, there was no air-conditioning until the 1950s. Tall windows allowed fresh air to flow through the building, even if it was as hot as blazes. Doors allowed even more air to circulate.