City Country State/Region Continent Since Ref. Volgograd Russia Volgograd Oblast Europe 1966 [446] Denver United States Colorado North America 1984 [447] San Antonio United States Texas North America 2008 [448] Kuala Lumpur Malaysia Federal Territory of Kuala Lumpur Asia 2010 [449] Chongqing China Municipality of Chongqing Asia 2015 [450] Ulsan South Korea Ulsan Metropolitan City Asia 2016 [451]