U.S. national zoo welcomes back visitors in Washington D.C.

Visitors line up to enter the Smithsonian's National Zoo in Washington, D.C., the United States, on May 21, 2021. The Smithsonian's National Zoo reopened in Washington D.C. on Friday at 20 percent of its full capacity, allowing guests to visit the nation's beloved giant pandas and many other wild animals. The zoo closed in March 2020 and reopened in July, then shut down again in November due to the COVID-19 pandemic. (Xinhua/Liu Jie)