Colosseo a Roma. (AP Photo/Gregorio Borgia)

New York. (AP Photo/Manu Fernandez)

San Francisco. (AP Photo/Eric Risberg)

Lisbona. (AP Photo/Armando Franca)

Montevideo, Uruguay. (AP Photo/Matilde Campodonico)

Ankara, Turchia. (AP Photo/Emrah Gurel)

Lago Michigan, Chicago. (AP Photo/Erin Hooley)

Chicago. (AP Photo/Charles Rex Arbogast)

Golden Gate Bridge, California. (Carlos Avila Gonzalez/San Francisco Chronicle via AP)

San Francisco, California. Justin Sullivan/Getty Images/AFP (Photo by JUSTIN SULLIVAN / GETTY IMAGES NORTH AMERICA / Getty Images via AFP)

Ciudad Juarez, Messico. REUTERS/Jose Luis Gonzalez

Gaza. REUTERS/Ibraheem Abu Mustafa

San Diego, California. REUTERS/Mike Blake

Havana. (Photo by YAMIL LAGE / AFP)

Caracas. (Photo by Federico PARRA / AFP)

Porto Alegres, Rio Grande do Sul state, Brasile. REUTERS/Diego Vara

Rabat. (Photo by FADEL SENNA / AFP)

Mosca, Russia. (AP Photo/Alexander Zemlianichenko)

Spain. (AP Photo/Alvaro Barrientos)

Greece. (AP Photo/Petros Giannakouris)

Mongolia. (AP Photo/Ng Han Guan)

Corinto. (Photo by Valerie GACHE / AFP)

Greece. (AP Photo/Thanassis Stavrakis)

Israele. EPA/ABIR SULTAN

Toronto, Canada. (Frank Gunn /The Canadian Press via AP)

Cagliari. ANSA

Maine, Usa. (Photo by Joseph Prezioso / AFP)

Doha city, Qatar. (Photo by KARIM JAAFAR / AFP)