Cardinal Stefaneschi presents the triptych itself to Saint Peter in Giotto's triptych
The Stefaneschi Triptych in the Vatican Pinacoteca contains the so-called Droste effect, named after a tin of cocoa that bore an image of itself bearing an image of itself.
If you look closely, on the central panel of the triptych Giotto depicted the patron of the work, Cardinal Stefaneschi, who is offering this very triptych to Saint Peter, on whose central panel he himself is depicted, offering the triptych
