The article discusses modern principles of illumination for classical architectural buildings, using examples of the illumination of St. Peter’s cathedral and of the basilica di Santa Maria Maggiore in Rome, piazza dei Signori in Vicenza, etc.). The desire to reflect truthfully the building tectonics by means of artificial illumination had engendered a variety of methods, none of which are ideal. The authors insist that when architectural landmark illumination projects are developed, it is not only light designers and architects who should take part but also architectural historians.