This charming circular chapel is one of architect Bramante's first works in Rome, where he arrived in 1499. Perfectly proportioned, it is surrounded by a portico with Doric columns and crowned by a dome. Despite its small size, it possesses the grandeur and rigour of an ancient structure. Behind the building, in a small chapel, the recess said to have held the cross of St Peter can be seen. From the church's esplanade a superb panoramic view stretches over the whole city.