Illuminated installations are seen in the old town of Warsaw, Poland, on Dec. 11, 2019. The Old Town of Warsaw has been decorated with colorful lights to mark the Christmas season. (Photo by Jaap Arriens/Xinhua)

A woman poses for photos beside an illuminated frame in the old town of Warsaw, Poland, on Dec. 11, 2019. The Old Town of Warsaw has been decorated with colorful lights to mark the Christmas season. (Photo by Jaap Arriens/Xinhua)

An illuminated installation is seen in the old town of Warsaw, Poland, on Dec. 11, 2019. The Old Town of Warsaw has been decorated with colorful lights to mark the Christmas season. (Photo by Jaap Arriens/Xinhua)

People walk past trees decorated with Christmas lights in the old town of Warsaw, Poland, on Dec. 11, 2019. The Old Town of Warsaw has been decorated with colorful lights to mark the Christmas season. (Photo by Jaap Arriens/Xinhua)

People enjoy Christmas lights in the old town of Warsaw, Poland, on Dec. 11, 2019. The Old Town of Warsaw has been decorated with colorful lights to mark the Christmas season. (Photo by Jaap Arriens/Xinhua)

Illuminated installations are seen in the old town of Warsaw, Poland, on Dec. 11, 2019. The Old Town of Warsaw has been decorated with colorful lights to mark the Christmas season. (Photo by Jaap Arriens/Xinhua)