City center of Istanbul, showing the original core of the metropolis, which includes the historic peninsula south of the Golden Horn and Galata north of the Golden Horn on the European side; with Üsküdar and Kadköy on the Asian side.
As a result of Istanbul's exponential growth during the 20th century, a significant portion of the city's outskirts comprised gecekondus (a Turkish term meaning built overnight), referring to the illegally constructed squatter buildings run rampant outside the centers of the country's largest cities.[83] At present, some gecekondu areas are being gradually demolished and replaced by modern mass-housing compounds.