Michaelangelo, Titian, and Fra Guglielmo della Porta. For the remainder of his life, Ligorio identified as both a Neapolitan citizen by birth and a Roman citizen. This recognition also increased the commissions and projects for which Ligorio was pursued, and made the papacy of Pius IV one of Ligorio's busiest times. This period also marked one of Ligorio's most prominent ventures into engineering. Papal duties included protecting the cities in its territory, which involved repairing fortifications in those cities. The duties of a Renaissance architect included consideration of engineering concerns, so Ligorio engaged in these renovations during his time as the Architect of the Vatican. He is particularly remembered for his role in the restoration of the Acqua Vergine, an ancient Roman aqueduct. Its malfunction was forcing Roman citizens to use the unsanitary water of the Tiber River. Ligorio demanded its reconstruction, which began in April 1561 and took approximately five years to complete. In the early 1560s, the pope turned his attention toward the completion of several projects in the Belvedere Court. Ligorio in particular focused on the Nicchione built by Bramante in the northern end of the Belvedere Court. He added a semicircular loggia, which ended up being used in many of Rome's festivals as a fireworks site. Ligorio's other contribution to the Belvedere Court was an open-air theater on the southern end, which was completed in May 1565. Unfortunately this theater was torn down in the eighteenth century and replaced by a wall. The Belvedere Court itself was used for a large tournament in March 1565 in honor of the marriage of the pope's nephew. The Nicchione space was designed to be viewed specifically from a window in the pope's apartment, framed like a painting. Another project requested by Pius IV in 1565 was the organization of Vatican archives. Ligorio was tasked with designing a structure to hold these records. Although little remains of this Archivio today, its architectural design suggests a brief departure from Ligorio's typical style (as exemplified by, for example, the extravagant Casino). Normally his facades were beautifully and intricately decorated in the mannerist tradition. This building, however, was notably utilitarian and modest. Ligorio was staying true to the purpose of the building and Pius' wishes by matching its design to its no-frills function. After the death of Michelangelo, Ligorio was appointed as the architect of the San Pietro church in May 1564. This