The Tempietto of San Pietro in Montorio is a small commemorative martyrium built by Donato Bramante , possibly as early as 1502 , in the courtyard of San Pietro in Montorio . The so-called Tempietto ( Italian : `` small temple '' ) is a small commemorative martyrium built by Donato Bramante , possibly as early as 1502 , in the courtyard of San Pietro in Montorio .