Democratic Azad Party (DAP) chief Das Nabi Azad said on Saturday that Kolkata is one of the cleanest cities in the country and you should give credit to Mamata Banerjee. Azad was in Kolkata to attend an event on Greek World Day. He told the paparazzi, “I want to congratulate Mamata Banerjee for making Kolkata one of the cleanest cities in the country.”