A house built on a rock on the river Drina is seen near the western Serbian town of Bajina Basta, about 160km (99 miles) from the capital Belgrade May 22, 2013. The house was built in 1968 by a group of young men who decided that the rock on the river was an ideal place for a tiny shelter, according to the house's co-owner, who was among those involved in its construction. (Photo by Marko Djurica/Reuters)

Bristol Zoo's baby gorilla Kukena holds onto his mother's arm as he ventures out of his enclosure at Bristol Zoo's Gorilla Island on May 4, 2012 in Bristol, England. The seven-month-old western lowland gorilla is starting to find his feet as he learns to walk having been born at the zoo in September. Kukena joins a family of gorillas at the zoo that are part of an international conservation breeding programme for the western lowland gorilla, which is a critically endangered species. (Photo by Matt Cardy)

The Resplendent Quetzal (Pharomachrus mocinno) is a bird in the trogon family. It is found from southern Mexico to western Panama (unlike the other quetzals of the genus Pharomachrus, which are found in South America and eastern Panama). It is well known for its colorful plumage.

This Strange Russian Cartoon Shows Mario's Nasty Side and bogatyr or vityaz is a stock character in medieval East Slavic legends (byliny), akin to a Western European knight-errant.

Several new species of peacock spider – just a few millimetres long and featuring extraordinary colours – have been discovered in Western Australia and South Australia. Jürgen Otto, a biologist from Sydney, has been researching the arachnids since 2005, and has gained a significant following online with his footage. He believes there are now 48 confirmed species of peacock spider within the Maratus genus, found across Australia but particularly in Western Australia – and many more awaiting confirmation. Here: Maratus Tasmanicus, one of seven new species of peacock spiders studied by the Sydney biologist Jürgen Otto. (Photo by Jürgen Otto)

Pro-Russian activists attack policemen guarding the burned trade union building in the southern Ukrainian city of Odessa on May 3, 2014. More than 30 people were killed in a “criminal” blaze in Ukraine's southern city of Odessa, as violence spread across the country during the bloodiest day since Kiev's Western-backed government took power. Ukraine's interior ministry said at least 31 people had died in the fire Friday, with local media reporting that pro-Russian militants were believed to have been in the burning building at the time. (Photo by Anatolii Stepanov/AFP Photo)

A German Air Force Officer sits astride a dead boar outside a house where he is stationed near the Western Front, in this 1918 handout picture. This picture is part of a previously unpublished set of World War One (WWI) images from a private collection. The pictures offer an unusual view of varied and contrasting aspects of the conflict, from high tech artillery to mobile pigeon lofts, and from officers partying in their headquarters to the grim reality of life and death in the trenches. The year 2014 marks the centenary of the start of the war. (Photo by Reuters/Archive of Modern Conflict London)