robert-hadley:Helicoidal staircase conceived by Jacobo Barozzi called il Vignola, 1565-1570. Capraro
robert-hadley:Helicoidal staircase conceived by Jacobo Barozzi called il Vignola, 1565-1570. Caprarola, Palazzo Farnese. FMR magazine, June 1989. -- source link