A cat sits on the empty Great Wall on February 23, 2021 in Beijing, China. Affected by the new coronavirus (COVID-19), the number of visitors to Mutianyu Great Wall in 2020 dropped by about 60%. (Photo by Lintao Zhang/Getty Images)

A member of a winter swimming club wears flippers during the celebration of Maslenitsa, also known as Pancake Week, a pagan holiday, marking the end of the winter, in Novosibirsk, Russia. (Photo by Alexandr Kryazhev/Sputnik/Profimedia)

Jerome Holcomb of Birmingham, Ala., posses for a photo atop a longhorn steer at the Fort Worth Stockyards Thursday, March 11, 2021, in Fort Worth, Texas. The mask mandate to prevent the spread of COVID-19 has been cancelled in Texas. Holcomb said he was tired of wearing a face mask so he came to visit Fort Worth after the Alabama governor extended the mask mandate in his home state. (Photo by L.M. Otero/AP Photo)

A biker carrying huge bags of recyclables travels on a street outside Phnom Penh, Cambodia on Saturday, March 27, 2021. (Photo by Heng Sinith/AP Photo)

“Kids of Sapa”. Four little beautiful Hmong girls from Lao Chai Village, near Sapa, Vietnam. (Photo and caption by Felipe Hanower/National Geographic Traveler Photo Contest)

Japanese college students look at cheerleaders during a job-hunting rally in Tokyo January 29, 2014. According to the rally organizers, about 1,500 students from vocational schools attend the rally to boost their morale ahead of their job hunt. (Photo by Yuya Shino/Reuters)

A new type of tandem at Alexandra Palace, London. (Photo by Fox Photos/Getty Images). June 1936

Two women lighting cigarettes on a tennis court in Essex, England circa 1930's. (Photo by Keystone View/FPG/Getty Images)