Pantheon site features

You come out of a lane into a small square and the front of it is a Greek temple that has no business being there. Eight huge grey granite columns stand in a row under a triangular pediment, with two more groups of four behind them, and the whole portico is darker and rougher than anything around it.

Behind the portico the building is a drum, and you cannot see that from the front. The temple face is flat against a cylinder, and the join is abrupt — a rectangular vestibule links one to the other.

Inside, the room is a sphere you are standing in the bottom of. The wall curves up, the dome curves over, and the height to the opening is the same as the width of the floor — a little over 43 metres each way.

The ceiling is sunk into squares. Five rings of 28 coffers climb and shrink towards the top, so the dome reads as getting lighter as it rises.

And at the top there is a hole with nothing in it. The oculus is 8.92 metres across, open to the sky, and the shaft of daylight through it moves across the wall as the day goes on. The floor beneath is coloured stone in squares and roundels — porphyry, giallo antico, granite and pavonazzetto — with 22 almost invisible holes in it for when it rains.

The oculus

8.92 metres across, open to the sky, the building's only light source.

The solstice disc

At the summer solstice the beam through the oculus projects an enormous luminous disc on the floor, of a diameter equal to the oculus's own.

The 28 coffers

Five orders of them, narrowing upward; 28 is considered a perfect number because it is 1+2+3+4+5+6+7.

The 22 holes

In a floor that is in good part original — porphyry, giallo antico, granite and pavonazzetto — taking the rain that comes through the oculus.

The inscription

The frieze names Agrippa. Turismo Roma calls it the original inscription; the reference work says Hadrian re-inscribed the new temple with Agrippa's original wording, which is why the building's date is unsettled.

The Byzantine icon

The Virgin and Child given by Emperor Phocas to Pope Boniface IV in 609, at the dedication of the temple to Christian worship.

Quod non fecerunt barbari

In 1625 the portico's bronze went to the baldachin of Saint Peter's and 80 cannons for Castel Sant'Angelo; Pasquino answered Quod non fecerunt barbari, fecerunt Barberini.

The royal tombs

Since 1870: Vittorio Emanuele II, Umberto I and Margherita di Savoia, with artists including Raffaello Sanzio.

The rose petals

Every year at Pentecost, a rain of rose petals falls from the oculus at the close of the celebration.