Istanbul is the largest city in Turkey and the heart of the country. In 2014, Istanbul has an estimated population of 14.2 million. Istanbul has grown very rapidly over the past one hundred years, although it has always had a large population. Istanbul has remained one of the largest cities in the world for most of its long history. In fact, Istanbul (then Constantinople) had a population between 400,000 and 500,000 in 500 AD, pushing out Rome as the largest ever city in the world at the time. ummer is generally hot with averages around 27ºC during the day and 18ºC at night. I have been jotting down the fascinating various facts while on my journey to Istanbul and I am having a great time doing stuff such as eating baklavas, a very tasty but insanely sugery food! It's like any big city, there are disparities between the rich and the poor. If you live in the beach areas, then life is good and spacious. If you live in somewhere like Topkapi, then its cramped and poor.