This is "The Baptism of Christ" by Piero della Francesca. Here, he has painted objects in proportion, so that they appear as we see them in real life. This emphasises the depth of the landscape, but also the harmony of the figures and natural features within it.
Christ stands in a shallow, winding stream as John the Baptist pours a small bowl of water over his head. Three angels in colourful robes witness the event. At this very moment the voice of God was heard – ‘This is my Son, whom I love; with him I am well pleased’ (Matthew 3: 16) – and the Holy Ghost, shown here as a dove flying over Christ’s head and towards us, descended upon him.
Piero used mathematical principles to order his simple design, creating a visually harmonious image. He set it within a landscape familiar to its original viewers, uniting them personally with this moment in the history of Christianity.
Notice how Piero has shown the water as though flowing away from us, and how we can see the pebbles of the riverbed in the foreground of the picture instead. This might be inviting us to imagine we are standing in the river, looking straight through the clear water.
The valley setting resembles the landscape around the town of Borgo Sansepolcro, encouraging worshippers to imagine the extraordinary moment occurring on their doorstep. The mountains in the distance, the stream and the walnut tree were features of the local landscape.
Piero made this picture for the church of San Giovanni Battista in Val d’Afra in his hometown of Borgo Sansepolcro – the walls and turrets in the distance are probably supposed to represent the town.
The Baptism of Christ hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.