The Bosporus is also called the Strait of Istanbul. It connects the Black Sea to the north, the Sea of ??Marmara and the Mediterranean Sea to the south, dividing Turkey into Asia and Europe. The total length of the strait is 30.4 kilometers, the widest point is 3.6 kilometers, the narrowest point is 708 meters, the deepest point is 120 meters, and the shallowest point is only 27.5 meters. Bosporus means "ox crossing" in Greek. Legend has it that Zeus, the king of gods in ancient Greece, once transformed into a majestic sacred bull and swam from this rough strait to the other side, carrying a beautiful human princess on his back, hence the name of the strait. The Bosporus is an important transportation thoroughfare connecting Europe and Asia, and it is also the first gateway for countries along the Black Sea to access the open sea. As trade and other exchanges between countries on the two continents continue to increase with the development of human civilization, its geographical location is of particular strategic significance. When King Darius I of the Persian Empire led his army to invade Europe in the 5th century BC, he built a pontoon bridge on the Bosporus. During the Crusades during the Eastern Roman Empire, they crossed here by boat and approached Jerusalem.