Gecekondu (houses that 20th century immigrants of Istanbul has built in one night) settlements are important elements for the development of the Istanbul’s urban structure. Istanbul has been a marine capital since very early centuries, and because of its location, Istanbul always has been an attraction for traders and therefore immigrants. Landscape and water are strong dominant entities that shape the development of the city. Byzantium, Ottoman and Turkish Republic periods in Istanbul, showed different behaviors in the organization of the settlements. Especially in Turkish Republic period, the organization behavior of the settlements had important change, with the industry and agricultural leap in Turkey. Istanbul has become an attraction mainly for the farm workers in eastern villages since early 20th century, which still continues. After these people migrated to Istanbul, though conditions led them to build and develop their own houses, without an infrastructure. This kind of development shows self-organization behavior and the assemblage of these houses emerges new kind of attributes, which contributes to the growth of Istanbul metropolitan area. Meanwhile, the transportation improvements, caused a transformation of these slum areas, where gated communities start to derive and force the change of the urban structure of the gecekondu (slum) settlements.