Buildings in Nogales, Mexico (R) are separated by a border fence from Nogales, Arizona, United Sates, October 9, 2016. Building a wall along the U.S.- Mexico border has been a contentious subject in this year's U.S. presidential election. In parts of California and Arizona, a wall already exists. It runs across rocky deserts, flowing sand dunes and miles of agricultural land. (Photo by Mike Blake/Reuters)

A model presents a creation during the Biofashion show, which features designs made from plants, recycled and natural materials, in Cali, Colombia, November 19, 2016. BioFashion is an environmental initiative that seeks to create awareness about the preservation and management of natural resources where new designers develop dresses made with living plants, flowers and organic elements. (Photo by Jaime Saldarriaga/Reuters)

Sami people from the Vilhelmina Norra Sameby, gather their reindeers herd in a corral for selection and calf labelling on October 27, 2016 near the village of Dikanaess, about 800 kilometers north-west of the capital Sweden. Sweden's Sami reindeer herders have more than hungry predators to worry about in the cold night, as the indigenous minority moves its flock to the winter pasture in the Nordic tundra. (Photo by Jonathan Nackstrand/AFP Photo)

A Colombian air force helicopter retrieves the bodies of victims from the wreckage of a plane that crashed into the Colombian jungle with Brazilian soccer team Chapecoense onboard near Medellin, Colombia, November 29, 2016. The chartered plane was carrying a Brazilian soccer team to the biggest match of its history when it crashed into a Colombian hillside and broke into pieces, killing 75 people and leaving six survivors, Colombian officials said Tuesday. (Photo by Jaime Saldarriaga/Reuters)

Vardzia is a cave monastery site in southern Georgia, excavated from the slopes of the Erusheti Mountain on the left bank of the Mtkvari River, thirty kilometres from Aspindza. The main period of construction was the second half of the twelfth century. The caves stretch along the cliff for some five hundred metres and in up to nineteen tiers. The Church of the Dormition, dating to the 1180s during the golden age of Tamar and Rustaveli, has an important series of wall paintings. The site was largely abandoned after the Ottoman takeover in the sixteenth century. Now part of a state heritage reserve, the extended area of Vardzia-Khertvisi has been submitted for future inscription on the UNESCO World Heritage List

Tommy Lindsey holds an enormous maple leaf that he found in Mount Vernon, Wash., October 28, 2013. Lindsey was walking with his family when he picked up the leaf that is more than two feet from stem to tip and more than 21 inches wide. (Photo by Frank Varga/The Skagit Valley Herald)

In this photo taken on Saturday, November 16, 2013, Mt. Etna, Europe's most active volcano, spews lava during an eruption as seen from Acireale, near the Sicilian town of Catania, Italy. (Photo by Carmelo Imbesi/AP Photo)

Chile's Javier Campillay drives past the burning car of Kazakhstan's Bauyrzhan Issabayev and Gabdulla Ashimov during the Dakar Rally 2014 Stage 2 from San Luis to San Rafael, on January 6, 2014. (Photo by Jean-Paul Pelissier/AFP Photo)