Swiss police officers stand beside of mock gates of the NEAT Gotthard Base Tunnel inside the event hall for the upcoming opening ceremony near the town of Erstfeld, Switzerland May 31, 2016. The celebrations of the opening of the Gotthard Base Tunnel will start on June 1, 2016. With a length of 57 km (35 miles) crossing the Alps, the Gotthard Base tunnel is the world's longest train tunnel. (Photo by Arnd Wiegmann/Reuters)

Performers dressed as Pikachu, a character from Pokemon series game titles, march during the Pikachu Outbreak event hosted by The Pokemon Co. on August 10, 2018 in Yokohama, Kanagawa, Japan. A total of 1, 500 Pikachus appear at the city's landmarks in the Minato Mirai area aiming to attract visitors and tourists to the city. The event will be held through until August 16. (Photo by Tomohiro Ohsumi/Getty Images)

A woman looks across as a gay parade participant poses for pictures during Gay Pride parade in Madrid, Spain, Saturday, July 2, 2016. Hundreds of thousands of people defied high temperatures and relative security concerns and turned out in Madrid to march in Saturday's LGTB Pride parade, one of the biggest in Europe, along the streets of the Spanish capital, just three weeks after members of the gay, lesbian, bisexual and transgender community were tragically victimized in a shooting massacre at a United States nightclub. (Photo by Daniel Ochoa de Olza/AP Photo)

Health workers wearing face masks spray disinfectant liquid on sacrificial animals amid concerns over the spread of the SARS-CoV-2 coronavirus that causes the pandemic COVID-19 disease ahead of the Muslim festival of Eid al-Adha at an animal market in Hyderabad, southern Pakistan, 21 July 2020. (Photo by Nadeem Khawar/EPA/EFE)

A demonstrator uses a slingshot during clashes with police at a protest against what they call the government's failure in handling the coronavirus disease (COVID-19) outbreak, in Bangkok, Thailand, August 7, 2021. (Photo by Soe Zeya Tun/Reuters)

Men give bananas to monkeys gathered on the side of the road as India remains under an unprecedented lockdown over the highly contagious coronavirus (COVID-19) on April 08, 2020 in New Delhi, India. Wild animals, including monkeys, are roaming human settlements in India as people are staying indoors due to the 21-day lockdown. (Photo by Yawar Nazir/Getty Images)

A girl walks past outside a house damaged by tidal waves at Meulaboh beach in Aceh province on July 12, 2020. (Photo by Chaideer Mahyuddin/AFP Photo)

Yueyaquan is a crescent-shaped lake in an oasis, 6 km south of the city of Dunhuang in Gansu Province, China. It was named Yueyaquan in the Qing Dynasty. According to measurements made in 1960, the average depth of the lake was 4 to 5 meters, with a maximum depth of 7.5 metres In the following 40 years, the depth of the lake continually declined. In the early 1990s, its area had shrunk to only 5,500 m2 with an average depth of 0.9 meter (maximum 1.3 meter). In 2006, the local government with help of the central government started to fill the lake and restore its depth; its depth and size have been growing yearly since then. The lake and the surrounding deserts are very popular with tourists, who are offered camel and 4x4 rides.