There was an announcement from Rome on February 1st, 1614 allows us to be certain about the date of the works and the plan of Maggi. It states, “Only one house is now to be destroyed to complete the opening up of the road designed from the Corso to Capo le Case…”. This is the straight line mentioned earlier. There was also a notarized deed from November of 1617 that spoke of the conduit of the Aqua Vergine from the Trevi fountain that had been recently built, which refers to the recent construction, or reconstruction of the old fountain. This means that the fountain can be dated to 1615, because it failed to follow Maggi’s plan. So the next question was, who did actually design the reconstruction of the Trevi. To find this out, it is important to note that Paul V was very fond of the style of the Moses Fountain, so in 1612 he had a larger model of the fountain constructed on the Janiculum, and then another smaller model of the fountain that was built by Vasanzio at the end of Via Giulia. These fountains were an addition to the rustic “Eagle Fountain”, that was already the showpiece of the Aqua Paola. So it only makes sense that for another one of his fountains, he would choose this type of design for the water feature.
So this all brings us right back to the notarized deed. This deed is one of those long and boring documents that record every minute detail of work that was undertaken to bring water to the fountains, as well as the checks that would be carried out on the premises of new customers. This deed was about an alteration, the following is the translation: “20 November 1617. The water pipes that were in the main conduit proper of the Aqua Vergine at the Trevi fountain in the quantity given below were moved from the place where they were before, that is to say from the terminal head of the conduit of the said water fountain beneath the house in which Giorgio Tintore resides; this head was demolished to enlarge and straighten the road that starts from Piazza Sciarra and goes to the church of San Nicola in Carcere [sic, but this should be San Nicola at Capo le Case]. The water pipes in question were placed, with the same capacity, in the terminal head of the said recently constructed conduit and, as is the commonly used term, “near to the first mouth of the said water” which is toward the Palace on the Quirinale Hill. This was done by order of the Hon. Lelio Biscia minister of the Rev. Papal Council and with the permission of the Architect Mr. Giovanni Vanzanten [ Vasanzio] appointed by His Lordship Paul V to the superintendence of the waters…”.
So this makes it more believable that the Moses-style façade fountain was the work of Vasanzio, but it was simply never built. Vasanzio was the architect for the Fountains during this time, and was in charge of directing the transfer of water popes from the Trevi during this stage.