After the catastrophic Tiber flood of 1557, hydraulic engineering projects became a major focus of urban reform in Rome during the 1560s. Massive public works were commissioned, namely the reconstruction of the acqueduct called Acqua Vergine. This project produced numerous discussions and writings by individuals, of both learned and practical backgrounds like the engineer Antonio Trevisi (d.1564), the jurist and Roman magistrate Luca Peto (1512-81) and the antiquarian Pirro Ligorio. In their writings, they proposed solutions influenced by their study of literary texts and investigations. The goal was to attract the prestigious patronage of pope Pius IV, in a context of conflicts due to the governance of Rome by the papacy and, on the other hand, the communal government. In 1560, Trevisi obtained the contract, but the project failed due to the difficulty of finding funds and to financial malpractice. Under pope Pius V, the repair resumed, and in 1570, the aqueduct was fully restored. Between Trevisi’s failure and the restoration of the Acqua Vergine, Ligorio’s contribution, preserved in his encyclopedia on ‘Roman antiquites’, lies completely overlooked. I propose to study it, showing some fundamental innovations put forward by the antiquarian in documenting through his drawings the restoration of the Acqua Vergine.