A hippopotamus performs during a show at the circus in Krasnoyarsk, Siberia, Russia, July 7, 2016. (Photo by Ilya Naymushin/Reuters)

Female Siberian tiger Dasha yawns in the new enclosure at the zoo in Duisburg, Germany, 30 March 2016. The new facility is three times larger than the old one and will be opened to the public on the same day. (Photo by Roland Weihrauch/EPA)

An elephant from Earl's Court Circus with a man in its mouth, 1928. P.S. All pictures are presented in high resolution.

Pigeons cool down at a public fountain on a hot summer day at University Plaza in downtown Bucharest, Romania, 10 June 2020. Temperatures in Bucharest reached 30 degrees Celsius. (Photo by Robert Ghement/EPA/EFE)

Yalena Leuliette, 7, of Greenbelt, Md., throws seeds from a cattail plant up in the air as she plays while visiting the Kenilworth Aquatic Gardens in northeast Washington, on Sunday, August 9, 2015. Leuliette visits the public garden with her parents a few times a year. (Photo by Jacquelyn Martin/AP Photo)

This photo taken on November 7, 2021 shows a panda falling from a platform as it plays in its enclosure after snowfall in Xian in China's northern Shaanxi province. (Photo by AFP Photo/China Stringer Network)

Gorillas at Royal Burgers’ Zoo, Arnhem, Netherlands, on November 28, 2013. (Photo by Vidi Photo/Startraks Photo New York)

Cave Diver, Anhumas Abyss, Bonito, Brazil: The Anhumas Abyss is an underground cavern with a crystal-clear lake below, more than 260 feet (79 m) deep. A visitor must enter through a narrow opening at the top of the chamber and rappel into the cave. Snorkeling and scuba diving in the lake reveal amazing scenery. Distinctive, conical limestone stalagmites and stalactites occupy the lake and the surrounding area, some reaching 65 feet (20 m) high. (Photo by Marcio Cabral/Nature’s Best Photography Awards 2017)