ENSuch large-scale construction action conducted in the first half of the 16th century connected to the reconstruction of the most important residences of king Sigismund I (Wawel, Piotrków, Niepołomice, Sandomierz, Lublin, Radom, and Vilnius) can only be likened to the great campaign of “bricking” of the Kingdom of Poland by Casimir the Great almost two hundred years earlier. Although a number of castles rebuilt by the Jagiellon cannot be equalled to over thirty buildings erected on the initiative of the last Piast on the Polish throne, the extent and breadth of these reconstructions enable us to make such a comparison. Moreover, construction works undertaken in the royal castles on the initiative of the starosts should as well be added to the investments of Sigismund I discussed in this article. They were connected with the need to provide residential facilities to the representatives of state administration working in the royal castles, which owing to a change in exercising power ceased to be visited by the monarch and lost the status of his residence. However, in legal, titular and symbolic respects they remained royal castles. Based on examples presented in the text we can state that Wawel castle, together with a chapel at its cathedral which remained a symbol of the construction activity of Sigismund I, should not overshadow a great number of equally impressive investments of the monarch in the field of residential and defensive architecture.