Surrounded by Turkey, Bulgaria, Georgia, Romania, Ukraine, and Russia, the Black Sea coast is lined with resort towns and ancient sights to explore while in port. It's also a very volatile region, though, where cruise itineraries fluctuate depending on the current conditions. Trips are typically one to two weeks, or part of longer, months-long European voyages. Since the Black Sea connects to the Mediterranean via the Bosporus and Dardanelles, many cruises start or end in Piraeus, Greece, or Istanbul, Turkey.