Piazza Navona
Previously the premises was the site of the Palace of St. Apollinare in the northern area of the Piazza Navona. Around 1417, Martin V gave Cardinal Branda da Castiglione the use of the Palazzo di Sant'Apollinare in the Piazza Navona. In 1455, Cardinal Guillaume d'Estouteville took up residence there, and built the Church of S. Agostino just to the east.