But the most important decorations are the series of 28 frescoes ascribed to the young Giotto along the lower part of the nave. Each bay contains three frescoes above the dado on each side of the nave, two frescoes in the east galleries beside the entrance, and two more on the entrance wall. Giotto used the "Legenda Maior", the biography of Saint Francis by Saint Bonaventure (1266) to reconstruct the major events in the life of Saint Francis. The prototype for this cycle may have been the (now lost) Saint Francis cycle by Pietro Cavallini in the church San Francesco a Ripa in Rome. The paintings are as vivid as if Giotto had been a witness to these events. According to Vasari, they were executed in the period between 1296 and 1304.