About a century before the tragic events of Beatrice Cenci, the Spanish complex on the Janiculum was enriched by the Tempietto built in the middle of the church courtyard. Although this little masterpiece by Bramante dates back to 1502, it had been commissioned earlier by the Spanish royal family to fulfill a vow for the birth of their first son, John, who died prematurely in 1497.
The building was built as a “martyrium” to mark the supposed site of St. Peter’s execution. It has an external round colonnade at the top of a short round flight of steps and this is crowned by a balustrade from the midst of which rises the little dome, partly modified by 17th century alterations. The round inner chamber contains an altar with St Peter’s statue sculpted by an unknown 16th century artist of the Lombard school. Beneath the chamber is a unadorned crypt where a slab on the floor protects the hole supposedly left by St Peter’s cross.