Kadıköy is an older settlement than most of those on the Asian side of the city of İstanbul. Relics dating to 5500-3500 BC (Chalcolithic period) have been found at the Fikirtepe Mound, and articles of stone, bone, ceramic, jewelry and bronze show that there has been a continuous settlement since prehistoric times. A port settlement dating from the Phoenicians has also been discovered. Chalcedon was the first settlement which the Greeks from Megara established on the Bosphorus, in 685 BC, a few years before they established Byzantium on the other side of the strait in 667 BC. Chalcedon became known as the 'city of the blind', the story being that Byzantium was founded following a prophecy that a great capital would be built 'opposite the city of the blind' (meaning that the people of Chalcedon must have been blind not to see the obvious value of the peninsula on the Golden Horn as a natural defensive harbour). Chalcedon changed hands time and time again, as Persians, Bithynians, Romans, Byzantines, Arabs, Crusaders, and Turks passed through the area, which was badly damaged during the Fourth Crusade and came into Ottoman hands in 1353, a full century before Constantinople. Thus, Kadıköy has the oldest mosque in İstanbul, built almost a century before the conquest of Constantinople in 1453. At the time of the conquest, Chalcedon was a rural settlement outside the protection of the city. It was soon put under the jurisdiction of the Constantinople courts, hence the name Kadıköy, which means Village of the Judge. In the Ottoman period, Kadıköy became a popular market for agricultural goods and in time developed into a residential area for people who would commute to the city by boat. The population was the typical Ottoman Constantinople mix of Armenians, Greeks, Jews and Turks. Kadıköy has several churches (Greek, Armenian, Serbian, Catholic, Protestant) and synagogues.
The major Haydarpaşa Terminal of the Turkish State Railways is located close to Kadıköy's center, serving east- and south-bound international, domestic and regional trains. Haydarpaşa Terminal was opened in 1908 as the terminus of the İstanbul-Baghdad and İstanbul-Damascus-Medina railways. This, along with the nearby Harem Bus Terminal, has services to Anatolia. The Söğütlüçeşme railway station, the next station to Haydarpaşa Terminal, is located also in Kadıköy. The terminus of the Metrobus line to European side of Istanbul is situated next to the railway station. The centre of Kadıköy today is the transportation hub for people commuting between the Asian side of the city and the European side across the Bosphorus. There is a large bus and minibus terminal next to the ferry docks. Ferries are the most dominantly visible form of transport in Kadıköy, and the central market area is adjacent to the ferry dock.
Shopping: Kadıköy is a busy shopping district, with a wide variety of atmospheres and architectural styles. The streets are varied, some being narrow alleyways and others, such as Bahariye Caddesi, being pedestrian zones. Turkey's biggest food market is there, starting next to the Osman Ağa Mosque, and has an immense turnover of fresh foods and other products from all around Turkey, including a wide range of fresh fish and seafood, olive oil soap, and so on. There are also modern shopping centres, most notably the large Tepe Nautilus Shopping Mall behind the center of Kadıköy, and pavements crowded with street vendors selling socks, pirated copies of popular novels, and other products. In the streets behind the main post office, there is a large number of well-known bookshops selling both new and second-hand books, craft-shops and picture-framers, and a number of shops selling music CDs and related ephemera such as film posters and t-shirts. Hard Rock and Heavy Metal music is sold in the arcade named Akmar Pasajı, where associated items are also sold. On Sundays this area becomes a large second-hand book and music street market. Being a crowded shopping district, Kadıköy has many buskers, shoe shine boys, glue sniffers and schoolchildren in the streets selling flowers, chewing gum and packets of tissues. At the top of the shopping district there is an intersection, with a statue of a bull, called Altıyol (Six Ways), where a road leads to the civic buildings and a huge street market called Salı Pazarı (Tuesday Market). The working-class residential districts of Hasanpaşa and Fikirtepe are located behind the civic buildings.