Visitors tour the National Museum in Warsaw which has reopened amid the COVID-19 outbreak in Warsaw, Poland, May 16, 2020. The National Museum in Warsaw has reopened to public visitors on May 12 after being closed for two months due to COVID-19. (Photos: Xinhua)

Visitors tour the National Museum in Warsaw which has reopened amid the COVID-19 outbreak in Warsaw, Poland, May 16, 2020. The National Museum in Warsaw has reopened to public visitors on May 12 after being closed for two months due to COVID-19.

A visitor tours the National Museum in Warsaw which has reopened amid the COVID-19 outbreak in Warsaw, Poland, May 16, 2020. The National Museum in Warsaw has reopened to public visitors on May 12 after being closed for two months due to COVID-19.

Photo taken on May 16, 2020 shows hand sanitizers prepared for visitors at the National Museum in Warsaw which has reopened amid the COVID-19 outbreak in Warsaw, Poland. The National Museum in Warsaw has reopened to public visitors on May 12 after being closed for two months due to COVID-19.

Visitors tour the National Museum in Warsaw which has reopened amid the COVID-19 outbreak in Warsaw, Poland, May 16, 2020. The National Museum in Warsaw has reopened to public visitors on May 12 after being closed for two months due to COVID-19.