Tyre, located on the Mediterranean coast in southern Lebanon, was founded, according to the ancient historian Herodotus, in about 2750 BC. At that time, it was an island a mile or so off the mainland. It had two fine harbors – one on the north side and one on the south side. It gradually became a major commercial center for trade throughout the Mediterranean. Two major exports from the region were the famed cedars of Lebanon and the purple dye derived from the murex sea snail. The dye became known as Tyrian purple or royal purple and was traditionally reserved for use by nobility. These exports, as well as the excellent and well-placed harbors, made Tyre and its citizens wealthy, and the object of envy. To fend off potential attackers, defensive walls up to 150 feet high were erected around the island city. Tyre successfully resisted various attacks by Egyptian forces. It also faced a 13-year siege by King Nebuchadnezzar II of Babylonia, which ended in a truce. After a siege of seven months, Alexander the Great conquered Tyre. He did so by building a stone causeway from the mainland. Over time, the causeway shifted water currents in the vicinity, leading to sediment accumulation. The island soon became a peninsula, permanently connected to the mainland. While the harbor on the north side was largely unaffected, the harbor on the south side became effectively unusable as a commercial port. During the Crusades, Tyre was captured by the Crusaders in 1124, but retaken by the Mamluks in 1291. Tyre has been impacted by the ongoing conflicts in the Middle East in recent times, but remains a large urban area and moderate-size port.