This work shows how augmented reality can help the comprehension of the geometric construction of the perspective in the Holy Trinity fresco (Masaccio, 1426) in the church of Santa Maria Novella in Florence,opening new scenarios in the demonstration of the subtle underlying geometric principles.There has been a long debate about the actual geometrical fidelity of the “fake architecture” painted in perspective in the Masaccio’s fresco. Recent studies demonstrated that Masaccio’s perspective is one of the best and commendable applications of the Brunelleschi's lesson about linear perspective and its geometric construction.We here use AR to follow step by step the geometric construction of Masaccio’s perspective.This approach takes advantage of the possibilities that AR offers to explore in realtime the relations between 3d and its 2d representations.