The town hall with the Mangia tower is seen in Siena, central Italy, January 29, 2016. (Photo by Max Rossi/Reuters)

A woman walks past graffiti in Beirut, Lebanon, Wednesday, May 4, 2016. Graffiti artists have been trying to re-engage disillusioned youth in a debate about the country's latest wave of political turmoil. (Photo by Hassan Ammar/AP Photo)

It might have been foggy in the Willamette Valley, but Cerridwen Martin was able to revel in a view of the top of the clouds from the summit of Spencer Butte in Eugene, Ore., on Tuesday, December 16, 2014. Martin was joined by Joe Martinson, right, for the 1.1 mile trek. Fog shrouded much of the city for most of the day. (Photo by Andy Nelson/AP Photo/The Register-Guard)

National Geographic has created “Air, Land & Sea: the 50 greatest wildlife photographs” exhibition. Here: CT4 Crocodile cave on the Salamat river. Set up with Nathan Williamson last chip rain came while we were with the nomads. (Photo by Michael Nichols/National Geographic)

A man poses with a hyena along a street in Lagos, Nigeria November 4, 2008. (Photo by Akintunde Akinleye/Reuters)

A Manipuri woman sells smoked and dry fish in Ima market - the world's largest all women market – in Imphal city, Manipur state, 06 January 2016. The 150-year-old Ima Keithel or “Mothers's market” complex, which is run exclusively by women and was damaged in the 04 January 2016 earthquake, is returning back to normal. Nine deaths have been reported from in and around Imphal due to falling debris. Imphal has a population of some 270,000 and people were jolted from their sleep and ran out of their homes in panic when the earth shook 04 January, reports say. (Photo by EPA/Stringer)

A sign advising to pray for rain hangs above an exhibit area at the 47th Annual World Ag Expo in Tulare, February 12, 2014. About a hundred years ago, when urban water systems were being developed throughout the state, the city of Sacramento wrote protections from metering into its charter, vowing that residents would always have the right to use as much water as they needed. But on Tuesday, the state's top water regulators released a framework for enforcing California's first statewide mandatory restrictions on urban water use – cuts of 25 percent for non-agricultural users ordered last week by Democratic Governor Jerry Brown as a devastating drought enters its fourth year. (Photo by David McNew/Reuters)

A vehicle leaves light trails in a long exposure photograph as it drives beneath the 500-metre Aperture Spherical Radio Telescope in Pingtang county, China. Construction on the device began in 2011 and is nearing completion. (Photo by Liu Xu/AP Photo)