The TEMPIETTO is a small commemorative tomb built by Donato Bramante around 1502, in the courtyard of San Pietro in Montorio.  It is considered a masterpiece of High Renaissance architecture and was one of Bramante's earliest commissions after moving to Rome. 

The Tempietto, one of the most harmonious buildings of the Renaissance, is meant to mark the traditional spot of St. Peter's martyrdom.  It is considered such a perfect building in every way that it's almost like a piece of sculpture - especially since it has little use as architecture.  Only 15 feet in diameter, the circular structure has all the grandeur of a great classical building, with emphasis on the harmony of all proportions. 

Bramante modeled the Tempietto after Rome's ancient Theater of Marcellus.  He had planned to set in within a colonnaded courtyard but that plan was never executed.  Instead it rests in the cloister of San Pietro in Montorio, and the very close surrounding buildings on 3 sides, allow an unobstructed view from only the front.    The model is depicted without the surrounding buildings.