Mermaid Hales Parcells geets children as she performs at the Virginia Aquarium in Virginia Beach, Va., Monday, April 3, 2017. The Aquarium presents a mermaid show one night each week during the month of April. (Photo by Steve Helber/AP Photo)

Participants lay down on a street covered by coloured powder during the annual Bangkok Color Run in Bangkok, Thailand April 1, 2017. (Photo by Athit Perawongmetha/Reuters)

A policewoman uses her mobile phone as navy honor guards stand near of a World War Two memorial during celebrations to mark Victory Day in the Black Sea port of Odessa May 9, 2014. Ukraine celebrates the 1945 victory over Nazi Germany during World War Two on May 9. (Photo by Gleb Garanich/Reuters)

A woman smokes marijuana during a Global March for Marijuana in Medellin, Colombia, May 5, 2018. The annual Global Marijuana March is taking place in over 100 cities across the world in an effort to raise awareness of the benefits of medical cannabis and to call for the legalization of marijuana. (Photo by Fredy Builes/Reuters)

Martin Rietze is a “volcano-chaser”, a particular breed of photographer who takes big risks for big shots. He was able to capture destructive and beautiful forces of nature at work on a trip to Japan in February 2013. His photos show the Sakurajima Volcano, an active volcanic who's record-breaking 1914 eruption sent lava flows across the island. (Photo by Martin Rietze/Guzelian)

“Bombay’s once ubiquitous Premier Padmini taxis were introduced in the 60s and are dwindling at an alarming rate. This follows a decree banning vehicles over 25 years old from the streets to be replaced with “modern alternatives”. In a few years these iconic workhorses will be gone from Bombay’s streets altogether. It is important to capture this before it disappears and I see the road wallah's cabs as the time capsules that allow me to do this”. – Dougie Wallace, Bombay India, March, 2013. (Photo by Dougie Wallace)

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.