Naturally, the architecture of each area is highly influenced by the climate and conditions of the place. In Iran, the northern area with the Hyrcanian jungles are built to have sloping roofs to resist the constant rainfall and use wood as the main material. In the arid central area of Iran what you find more than anything is clay soil so the houses are built with bricks and under the level of the street to overcome the heat. In the mountain areas the houses are built with stones, the only thing that can survive the harsh weather and cold. After the advent of Islam, however, the architecture of Iran underwent some conceptual changes. One was the belief in the separation of Public (Birouni) and Private (Andarouni) spaces and the other was the utilization of various arts for the decoration of the façade and other parts of the constructs. Although highly decorative, you won’t find any unneeded place in Persian Architecture, the functional aspect of the house was always considered to be superior to all other functions.