This spectacular Basilica is one of the largest churches in the world, and the largest built in brick, making human figures seem tiny in its lofty Gothic arches. The building was originally a civic space, and in the left nave is the world's longest indoor meridian line, 66.8 metres/219.2 feet—exactly 1/600,000th of the earth's circumference—dedicated in 1656 by the Italian astronomer Gian Domenico Cassini. The sun's light shines from a hole 27 metres above ground and its position on the line exactly marks the days and seasons. Bas-reliefs over the side portals are by Properiza de' Rossi, one of the few female sculptors of the Renaissance. San Petronio is not the cathedral of Bologna, which is nearby.

I had begun this painting almost twenty-five years earlier and it had lain around my studio in its first stages since then; I spent a further three weeks finishing it. The style is reflective of my more architectural focus at the time. I had been flying 737s for a Belgian airline based in Milan for the spring of 1994, and Bologna was one of our overnight bases, as well as other Mediterranean cities. Sarah, sitting on the right, was with me on this trip.