This is a quick and easy cheap shuttle to take you from Gaziantep airport to downtown Gaziantep…read morewalking distance from the castle. Much cheaper than a taxi. Havaş is a chain that exists in Istanbul as well. Very convenient and better than dealing with a tax in Istanbul. I rather like many of the taxi drivers in Gaziantep. You pay after you sit down inside the bus/van. There is a guy with a wad of bills and tickets that will come to you at your seat in the bus.