Visitors walk into pollution pods, an immersive art installation which encourages visitors to walk through the pods and experience the daily reality of air pollution lived by millions, during the UN Climate Change Conference COP25 at the 'IFEMA - Feria de Madrid' exhibition centre, in Madrid, on December 2, 2019. - Spain's Socialist government offered to host this year's UN climate conference, known as COP25, from December 2 to December 13, 2019, after the event's original host Chile withdrew last month due to deadly riots over economic inequality. (Photo by GABRIEL BOUYS / AFP)