This episode shows the route from Van to Diyarbakır. Diyarbakır is a major city in the Southeastern Anatolia region of Turkey. The city is situated on the banks of the River Tigris, and is the seat of Diyarbakır Province. With a population of 545,000 Diyarbakır is the second-largest city in Turkey's South-eastern Anatolia region, after Gaziantep. Within Turkey, Diyarbakır is famed for its culture, folklore and its watermelons. Diyarbakır has a large Kurdish population, prompting some sources to describe it as the "unofficial capital" for the country's Kurdish citizens, of the country's Kurdish-speaking region. Diyarbakır is surrounded by an intact, dramatic set of high walls of black basalt forming a 5.5 km circle around the old city. There are four gates into the old city and 82 watch-towers on the walls, which were built in antiquity, restored and extended by the Roman emperor Constantine in 349. Diyarbakır boasts numerous medieval mosques and madrassahs including: Ulu Camii ("Great Mosque") built in the 11th century. The mosque, one of the oldest in Turkey, is constructed in alternating bands of black basalt and white limestone. (The same patterning is used in the 16th century Deliler Han Madrassah, which is now a hotel. The adjoining Mesudiye Medresesi was built at the same time as was another prayer-school in the city Zinciriye Medresesi.