Even in ancient times the Quirinal and Viminal Hills were sparsely populated . . . and during the Renaissance and Baroque eras its character was predominately suburban – open countryside dotted with a few aristocratic villas that overlooked vineyards and gardens. Only the narrow east-west thoroughfare that ran along the crest of the Quirinal Hill (from the Piazza del Quirinale to the Porta Pia) attracted concentrated construction, in the form of four Baroque churches in the space of four blocks. Today that sequence of churches . . . is little visited by tourists, but it is a place of pilgrimage among architects and students of architecture . . .