The ruins of the castle of the Mazovian princes were then incorporated into a new fortified manor built by King Sigismund III Vasa for his son, future King Władysław IV Vasa. However, there is little evidence that the residence was ever used by the young prince, who spent much of his youth either at his father's court. According to Adam Jarzębski's "Short Description of Warsaw" from 1643, the entrance to the Ujazdów Castle was adorned with four marble lions ("I lwy cztery generalne, Między nimi, naturalne, Właśnie żywe wyrobione, A z marmuru są zrobione; Nie odlewane to rzeczy, Mistrzowską robotą grzeczy"). Between 1659 and 1665, the building housed the mint of Titus Livius Boratini, who there struck his famous "boratynka", a type of copper coin.