Byzantine treasures, the legacy of Emperor Justinian, stories of Ottoman sultans and the sacking of the city by the Crusaders all contribute to Istanbul's irresistible appeal. You'll sail round trip from the city with the opportunity to discover its many fascinating mosques, museums and markets. In between, this cruise goes in search of other cities less well known. Around the Black Sea, vines and spa towns thrive under a sub-tropical sun. There are beaches and promenades lined with flowers to match any in the Mediterranean. Among the highlights are places that have changed the course of history: Yalta, the Crimean peninsula and the valley where the Charge of the Light Brigade took place.