Originally designed by Brunelleschi (1420), the hospital was completed and modified by Francesco della Luna. It was inaugurated in 1445 though the facade, with its wonderful nine-arched portico, had already been completed six years earlier, giving harmony to the square and inspiring the similar porticos in front of the Church of SS.Annunziata (completed by Giovan Battista Caccini in the early 17th century) and the Confraternita dei Servi di Maria, also known as the Loggia dei Servi, built a century later on the opposite side of the square by Antonio da Sangallo the Elder and by Baccio d'Agnolo (1516-25).
The pendatives that can be seen between the nine harmonious arches supported on columns with Corinthian capitals were later decorated with the famous tondos in glazed terracotta of figures of babies, the work of Andrea della Robbia (1463), the pupil and nephew of Luca: this addition tends to slightly alter the clear contrast of the grey stone against white plaster of Brunelleschi's design. The two Puttos on the left are 19th century imitations.