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. (Photos: 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.

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.

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.

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.

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.