Illuminated stairs are seen in the Fountain Park in Warsaw, Poland, Dec. 16, 2020. The Fountain Park in Warsaw has been illuminated with decorative Christmas lighting and two special installations have been made to thank medical workers battling the COVID-19 epidemic.Photo:Xinhua

A siren, which is the symbol of the city of Warsaw, is illuminated next to a heart and the words "Thank You Medics" in Warsaw, Poland, Dec. 16, 2020. The Fountain Park in Warsaw has been illuminated with decorative Christmas lighting and two special installations have been made to thank medical workers battling the COVID-19 epidemic.Photo:Xinhua

Illuminated trees are seen in the Fountain Park in Warsaw, Poland, Dec. 16, 2020. The Fountain Park in Warsaw has been illuminated with decorative Christmas lighting and two special installations have been made to thank medical workers battling the COVID-19 epidemic.Photo:Xinhua

Illuminated stairs are seen in the Fountain Park in Warsaw, Poland, Dec. 16, 2020. The Fountain Park in Warsaw has been illuminated with decorative Christmas lighting and two special installations have been made to thank medical workers battling the COVID-19 epidemic.Photo:Xinhua

A siren, which is the symbol of the city of Warsaw, is illuminated next to a heart and the words "Thank You Medics" in Warsaw, Poland, Dec. 16, 2020. The Fountain Park in Warsaw has been illuminated with decorative Christmas lighting and two special installations have been made to thank medical workers battling the COVID-19 epidemic.Photo:Xinhua

A building in the Old Town is seen through an illuminated Christmas ball in Warsaw, Poland, Dec. 16, 2020. The Fountain Park in Warsaw has been illuminated with decorative Christmas lighting and two special installations have been made to thank medical workers battling the COVID-19 epidemic.Photo:Xinhua