Ottaviano Nonni, called Il Mascherino, was an Italian architect, sculptor, and painter born in Bologna. He was the architect of the Quirinal Palace under Pope Gregory XIII. His other works include the churches of San Salvatore in Lauro (1591), Santa Maria in Traspontina, the Bandini Chapel in San Silvestro al Quirinale, and the oval plan-design for the church of Santo Spirito in Sassia.
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