The Kizilirmak, the longest river (1,182 kilometers) in Turkey, starts in the eastern part of Turkey and makes a great circle in Central Anatolia before flowing into the Black Sea. It was called the "Red River" due to the soil that colored the water. This river, known to the Hittites as "Marassantiya" and to the Greeks and Romans as "Hallys", was historically important. According to Herodotus, the Hallys divided Anatolia into two major parts, "the Black Sea shores" and "the land facing Cyprus," and formed a natural border between the Persian and the Lydian empires.
Before his campaign against Persia, the Lydian King Croesus consulted an oracle that predicted, "If you cross the Hallys, a great empire will be destroyed." Croesus interpreted this in a favorable way and had the Greek philosopher and physicist Thales diverts the Hallys so that Croesus' armies could cross the dry river bed. However, this ingenious solution did not save him from defeat at the hands of his enemy, Cyrus the Great of Persia.