US President Barack Obama (L) tours the Colosseum with guide Barbara Nazzaro, technical director and architect of the Colosseumin on March 27, 2014 in Rome. During his visit to the Eternal City, Obama met with Pope Francis at the Vatican, Prime Minister Matteo Renzi, the European Union's youngest government leader -- and President Giorgio Napolitano, as well as going on a private guided tour of the Colosseum.  AFP PHOTO / Saul LOEB        (Photo credit should read SAUL LOEB/AFP/Getty Images)