Cuban President Raul Castro (2-R) and Argentine President Cristina Fernandez de Kirchner (R) attend Pope Francis' mass at Revolution Square in Havana on September 20, 2015. Pope Francis will give mass on Revolution Square, the biggest event of his trip to Cuba, with nearly a million people expected to attend. The pontiff's eight-day tour will also take him to the United States. AFP PHOTO / FILIPPO MONTEFORTE