Turkey lies at the crossroads between Europe and Asia; it stretches from the northeast end of the Mediterranean Sea in southeast Europe and southwest Asia. To the north is the Black Sea and to the west is the Aegean Sea. Its neighbours are Greece and Bulgaria to the west, Russia, Ukraine, and Romania to the north and northwest (through the Black Sea), Georgia, Armenia, Azerbaijan, and Iran to the east, and Syria and Iraq to the south. The Dardanelles, the Sea of Marmara, and the Bosporus divide the country. Dominated by Greeks, Persians, and Romans in turn throughout the classical era, what is now Turkey was once the seat of the Byzantine Empire. After the Ottoman Empire fell in 1918, Turkey transformed itself into the vibrant, modernising, secular state it is today.