Pentecost is the Sunday that commemorates the descent of the Holy Spirit on the apostles, as recounted in Acts 2:1-41 (cached). In ancient and medieval images we see only the apostles (example), but at the end of the medieval period we start to see the Virgin Mary as the focal point of the group, as at left and in this example. Her presence at the Pentecost event is suggested by Acts 1:14 (cached).
The main features that characterize a Pentecost image are the tongues of fire that come upon the apostles and a dove representing the Holy Spirit.
Santo Spirito in Sassia, Rome, has magnificent frescoes of Pentecost in the chancel, the vault of a chapel, and an altarpiece.
Feast day: 50 days after Easter
At left, Roman painting circa 1573
Altarpiece in Estaing, France
Spanish painting from 1507