People walk through illuminated Christmas installations in Warsaw, Poland on Dec. 5, 2020. With the lighting up of a large Christmas tree on the Castle Square in Warsaw, Saturday marked the official opening of the Christmas season. (Photo by Jaap Arriens/Xinhua)

Photo taken on Dec. 5, 2020 shows illuminated Christmas installations in Warsaw, Poland. With the lighting up of a large Christmas tree on the Castle Square in Warsaw, Saturday marked the official opening of the Christmas season. (Photo by Jaap Arriens/Xinhua)

People take photos of the illuminated Christmas tree on the Castle Square in Warsaw, Poland on Dec. 5, 2020. With the lighting up of a large Christmas tree on the Castle Square in Warsaw, Saturday marked the official opening of the Christmas season. (Photo by Jaap Arriens/Xinhua)

Photo taken on Dec. 5, 2020 shows illuminated Christmas installations in Warsaw, Poland. With the lighting up of a large Christmas tree on the Castle Square in Warsaw, Saturday marked the official opening of the Christmas season. (Photo by Jaap Arriens/Xinhua)