Two guards perform an execution in China, one holding the gun, the other holding a mask over the victim's face. (Photo by General Photographic Agency/Getty Images). Circa 1925

Mounted cop in action on Tremont Street in Boston, Massachusetts, 1920 – 1929 (approximate). (Photo by Leslie Jones)

An enthusiast dressed as a zombie takes part in the annual Zombie Walk festival in Prague June 1, 2013. (Photo by David W. Cerny/Reuters)

A large bull walrus returns to the shores of Prins Karl Forland after diving and feeding on clams. (Photo by Paul Nicklen/National Geographic). Svalbard, Norway, 2011

Award-winning photographer Alex Bernasconi has captured thousands of images – from hiding hippos to wandering zebras – in his travels across Africa. His amazing work features in a new edition of his book Wild Africa. These amazing pictures create a snapshot of the life of some of the planet’s most spectacular animals and natural habitats. Photo: “Wild Africa”. (Photo by Alex Bernasconi)

An Animal Liberation Victoria activist cries as she holds a dead animal at Federation Square on October 1, 2013 in Melbourne, Australia. Over 200 activists gathered with the bodies of deceased animals to publicly grieve their deaths. Animal Liberation Victoria is against the treatment of animals as “property” an promotes a vegan lifestyle. (Photo by Graham Denholm)

In an observance of Epiphany, Russian Orthodox believers swim in an icy pond outside Nizhny Novgorod, Russia. (Photo by Olga “Zwezdochka”)

These stunning coloured images show detailed x-ray images of everything from skulls to light bulbs. Artist Paula Fontaine, from Westminster Massachusetts, created the images using a process called digital map painting. To create the images the x-ray emission source – the head of the machine on an arm which focuses the beam – is placed over the object. Paula then retreats behind a shielded screen before activating the x-ray exposure. Here: Brain storm, conceptual composite X-ray. (Photo by Paula Fontaine/Barcroft Media)