A visitor poses in front of a large Santa Claus decoration at the "Christmas Market Municipal Cave", an underground Christmas market in Valkenburg, the Netherlands, on Dec. 8, 2019. The Christmas Market Municipal Cave is held in the marlstone corridors of the Municipal Cave in Valkenburg in the southeastern Netherlands. The market lasts from Nov. 15 to Dec. 29 this year. (Xinhua/Lin Liping)

Photo taken on Dec. 8, 2019 shows the "make a wish" balls on Christmas trees at the "Christmas Market Municipal Cave", an underground Christmas market in Valkenburg, the Netherlands. The Christmas Market Municipal Cave is held in the marlstone corridors of the Municipal Cave in Valkenburg in the southeastern Netherlands. The market lasts from Nov. 15 to Dec. 29 this year. (Xinhua/Lin Liping)

People view colorful lights at the "Christmas Market Municipal Cave", an underground Christmas market in Valkenburg, the Netherlands, on Dec. 8, 2019. The Christmas Market Municipal Cave is held in the marlstone corridors of the Municipal Cave in Valkenburg in the southeastern Netherlands. The market lasts from Nov. 15 to Dec. 29 this year. (Xinhua/Lin Liping)

People visit merchandise stands at the "Christmas Market Municipal Cave", an underground Christmas market in Valkenburg, the Netherlands, on Dec. 8, 2019. The Christmas Market Municipal Cave is held in the marlstone corridors of the Municipal Cave in Valkenburg in the southeastern Netherlands. The market lasts from Nov. 15 to Dec. 29 this year. (Xinhua/Lin Liping)

Photo taken on Dec. 8, 2019 shows the entrance of the "Christmas Market Municipal Cave", an underground Christmas market in Valkenburg, the Netherlands. The Christmas Market Municipal Cave is held in the marlstone corridors of the Municipal Cave in Valkenburg in the southeastern Netherlands. The market lasts from Nov. 15 to Dec. 29 this year. (Xinhua/Lin Liping)

People visit a merchandise stand at the "Christmas Market Municipal Cave", an underground Christmas market in Valkenburg, the Netherlands, on Dec. 8, 2019. The Christmas Market Municipal Cave is held in the marlstone corridors of the Municipal Cave in Valkenburg in the southeastern Netherlands. The market lasts from Nov. 15 to Dec. 29 this year. (Xinhua/Lin Liping)