People ice skate at the Grand Palais in Paris, Monday, Dec. 17, 2018. The Grand Palais skating rink opens to the public during Christmas holidays and is the largest temporary ice rink created in France. (AP Photo/Christophe Ena)

People ice skate at the Grand Palais in Paris, Monday, Dec. 17, 2018. The Grand Palais skating rink opens to the public during Christmas holidays and is the largest temporary ice rink created in France. (AP Photo/Christophe Ena), APTOPIX

People ice skate at the Grand Palais in Paris, Monday, Dec. 17, 2018. The Grand Palais skating rink opens to the public during Christmas holidays and is the largest temporary ice rink created in France. (AP Photo/Christophe Ena)

This picture taken on December 17, 2018, shows a general view of people on the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of people on the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of people on the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of people on the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

This picture taken on December 17, 2018, shows a general view of people on the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)

German Defence Minister Ursula von der Leyen disembarks an Airbus A310 of the German Air Force as she arrives for a visit of German soldiers at Camp Marmal in Mazar-i-Sharif, northern Afghanistan, on December 17, 2018. - Von der Leyen arrived in Afghanistan for the traditional troops visit before Christmas. (Photo by Kay Nietfeld / POOL / AFP)

This picture taken on December 17, 2018, shows a general view of people on the ice skating rink hosted at the glass-roofed central hall of the Grand Palais in Paris. (Photo by STEPHANE DE SAKUTIN / AFP)