 He used a pre-existing tower (the Torre dei Leoni), which was part of the defensive walls, at that period very much to the south of the present ones, running, roughly speaking, along the line of the present Corso Giovecca and Viale Cavour.The tower was joined by curtain walls to another three newly built for this project.Between the Este residence and the new fortress was built an aerial passageway (perhaps in wood) to allow people to flee from one to the other.