Here's a photo from last year's lighting of the tree.
On December 9, 2017 the Vatican celebrated the lighting of the Nativity and Christmas tree with carol singing, a spirit of joy and gifts. The Nativity scene was donated by the Italian abbey of Montevergine and the 93-foot-tall fir tree was donated by Poland. The tree is adorned with ornaments crafted by children being treated for cancer from several Italian hospitals.
Photograph by Antoine Mekary for Aleteia