A lightning strikes St Peter's dome at the Vatican on February 11, 2013. Pope Benedict XVI announced today he will resign as leader of the world's 1.1 billion Catholics on February 28 because his age prevented him from carrying out his duties – an unprecedented move in the modern history of the Catholic Church. (Photo by Filippo Monteforte/AFP Photo)

A couple looks at their flooded street from behind their home's window in La Plata, in Argentina's Buenos Aires province, where at least 35 people were killed by flooding overnight, on April 3, 2013. (Photo by Natacha Pisarenko/Associated Press)

The sign above the door of restaurant and hotel “Am Paulusbogen” is partially submerged in the flooded centre of the Bavarian town of Passau, about 200 km (124 miles) north-east of Munich June 3, 2013. (Photo by Michaela Rehle/Reuters)

Swedish brown bears “Fred” and “Frode” play in the snow on January 30, 2014 at the Natur- und Umweltpark (NUP) animal park in Guestrow, northeastern Germany. Despite of icy temperatures, the bear brothers took a break from their winter rest. (Photo by Bernd Wuestneck/AFP Photo/DPA)

A student from the General Yermolov Cadet School takes part in weapons training during a two-day field exercise near the village of Sengileyevskoye, just outside the south Russian city of Stavropol April 13, 2014. The General Yermolov Cadet School in the southern Russian city of Stavropol is a state-run institution that teaches military and patriotic classes in addition to a normal syllabus. (Photo by Eduard Korniyenko/Reuters)

A man braces his umbrella while walking through the snow on February 13, 2014 in New York City. Heavy snow and high winds made for a hard morning commute in the city. (Photo by John Moore/Getty Images)

An undated archive picture shows a dog pulling a Belgian machine gun at an unknown location in northern France. A Viscount in the Armoured Cavalry Branch of the French Army left behind a collection of hundreds of glass plates taken during World War One (WWI) that have never before been published. The images, by an unknown photographer, show the daily life of soldiers in the trenches, destruction of towns and military leaders. The year 2014 marks the 100th anniversary of the start of WWI. (Photo by Collection Odette Carrez/Reuters)

Women practice yoga at a lotus pond in Tiande Lake on the International Yoga Day on June 21, 2017 in Taizhou, Jiangsu Province of China. (Photo by VCG/VCG via Getty Images)