One of the world’s great public spaces, the piazza was laid out by Gian Lorenzo Bernini between 1656 and 1667 for Pope Alexander VII. Seen from above, it resembles a giant keyhole with two semicircular colonnades, each consisting of four rows of Doric columns, encircling a giant ellipse that straightens out to funnel believers into the basilica. The effect was deliberate – Bernini described the colonnades as representing ‘the motherly arms of the church’. The 25m obelisk in the centre was brought to Rome by Caligula from Heliopolis in Egypt and later used by Nero as a turning post for the chariot races in his circus.

The scale of the piazza is dazzling: at its largest it measures 340m by 240m; there are 284 columns and, on top of the colonnades, 140 saints. In the midst of all this the pope seems very small as he delivers his weekly address at noon on Sunday.