There is a totally invisible glass door and the mysterious lights are just reflections on the glass pane. I'm sure that either on the ceiling or on the walls of Ca' Foscari, there are light fixtures that resemble flying saucers. The University of Venice, Ca' Foscari, offers tours of this historic palazzo. For information, you can contact: cafoscaritour@unive.it or visit: www.unive.it/tour