LONDON, ENGLAND - APRIL 19:  A replica of the Triumphal Arch at Palmyra is unveiled by the Mayor of London, Boris Johnson, at Trafalgar Sq on April 19, 2016 in London, England. The 2000 year old arch in the Syrian city of Palmyra was destroyed by Islamic State forces in October 2015. The replica is intended as an act of defiance against ISIS.  (Photo by Chris Ratcliffe/Getty Images)