This cycle of tempera frescoes are his masterworks .
The left transept was decorated by the Sienese painter Pietro Lorenzetti and his workshop between 1315 and 1330 ( attributed by Vasari to Pietro Lorenzetti and also ( wrongly ) to Giotto and Puccio Capanna ) .
This cycle of tempera frescoes are Giotto 's masterworks .
The left transept was decorated by the Sienese painter Pietro Lorenzetti and his workshop between 1315 and 1330 ( attributed by Vasari to Pietro Lorenzetti and also ( wrongly ) to Giotto and Puccio Capanna ) .