Built following the plague of 1493-1501, it is now part of the War Memorial. It is an octagonal construction, which is reminiscent of Bramante’s architecture.

The floor consists of cobalt blue and orange ceramic tiles, with a simple blue frame. The decorative repertoire includes floral and geometric motifs, animals, and the heads of ladies and knights in caricature profiles. The coat of arms of the Piccolomini family suggests that the floor was laid during the pontificate of Pius III.