Long-tailed mayflies (Palingenia longicauda) at Tisza river near Tiszainoka 135km (84 miles) southeast of Budapest, June 23, 2013. Millions of these short-lived mayflies engage in a frantic rush to mate and reproduce before they perish in just a few hours during “Tiszaviragzas” or Tisza blooming season from late spring to early summer every year. (Photo by Laszlo Balogh/Reuters)

Son doong cave is a cave in Phong Nha-Kẻ Bàng National Park, Bố Trạch district, Quảng Bình Province, Vietnam. Currently the biggest known cave in the world, the cave is located near the Laos-Vietnam border. Inside is a large, fast-flowing underground river.
In early August 2013, the first tourist group explored the cave on a guided tour at a cost of US$3,000 each. The group had six members from Australia, Norway, Russia and USA and spent 7 days and 6 nights for the tour. Next exploration trips will be arranged.

Two holy men with a decorative faces and headdresses, taken in Kathmandu, Nepal. Wandering through the cities and forests of Nepal are the holy men, or Sadhus, who have left all materialistic pleasures behind to live a life devoted to God. Their appearances vary from brightly coloured face paints, and decorations, to minimalistic practical clothing, but they all represent the fundamental values and meanings of Hinduism. Danish photographer Jan Moeller Hansen visited the ancient capital city of Kathmandu between 2013 and 2016 and documented the mysterious holy wanderers. (Photo by Jan Moeller Hansen/Barcroft Images)

An armed man gestures in front of the police headquarters in Slaviansk, April 12, 2014. At least 20 armed militants wearing mismatched camouflage outfits took over the police and security services headquarters in the eastern city of Slaviansk seizing hundreds of handguns. (Photo by Gleb Garanich/Reuters)

An Iraqi man cooks traditional Masgouf fish on a barbecue for sale in the Karada market July 02, 2014. Masgouf, one of the national dishes of Iraq is a grilled carp seasoned with olive oil, rock salt, tamarind and ground turmeric. (Photo by Scott Nelson for the Washington Post)

A statue of a man sleepwalking in his underpants is surrounded by snow on the campus of Wellesley College, in Wellesley, Mass., Wednesday, February 5, 2014. The sculpture entitled “Sleepwalker” is part of an exhibit by sculptor Tony Matelli at the college's Davis Museum. (Photo by Steven Senne/AP Photo)

A man carries the body of his son for burial after he was killed when a rooftop of his house collapsed due to heavy rain in the outskirts of Peshawar, Pakistan April 27, 2015. A severe storm in northwest Pakistan, dubbed a “mini-cyclone”, has killed 44 people and injured more than 200, officials said, raising their previous death toll. (Photo by Fayaz Aziz/Reuters)

A man wearing an armor attends a reenactment of the Battle of Agincourt, in Agincourt, northern France, Saturday, July 25, 2015. The French are hosting a reenactment of the clash with England this weekend. More than 800 people in Medieval garb are gathering at the site to commemorate the battle, which was a turning point in the Hundred Years' War. (Photo by Thibault Camus/AP Photo)