When Old Saint Peter's was torn down and rebuilt in the sixteenth and seventeenth centuries, one of the few monuments to be preserved intact and reinstalled in its original location in the new basilica was the set of great bronze doors standing in the central portal. In the literature on Filarete's doors, the history of the Porta Argentea has often been noted, but the ceremonial function of the site has hardly been considered. This chapter argues that this context is in fact fundamental for understanding Filarete's design. In Filarete's day, representations of the martyrdoms of Paul and Peter were visible in several places in the basilica. Ciriaco was one of the most original and eccentric interpreters of the ancient past of his day and his participation in the design of Filarete's doors could go a long way towards explaining their unusual features.