[Pope Francis welcomes a group of Syrian refugees after landing at Ciampino airport in Rome following a visit at the Moria refugee camp on April 16, 2016 in the Greek island of Lesbos]Pope Francis, who visited the Greek migrant hotspot island of Lesbos Saturday, took three Syrian families with him on the papal plane back to the Vatican, describing the move as a "humanitarian gesture... (but) a drop in the ocean."