Purcell replies Altschuler's brilliant suggestion has pluses and minuses. One consideration makes it more telling than he knows: the spectacular towers of Jerusalem as rebuilt by King Herod the Great. The historian Josephus described Jerusalem at the time of the appalling siege by the Romans in AD70, which resulted in its complete destruction, along with Herod's magnificent Temple.

Three enormous towers were key landmarks, joined by a remarkable network of fortification walls, themselves punctuated by numerous smaller towers, and by the Antonia Fortress. Something of the grandeur of these structures appears from excavations at Herod's palace-fortress at Greater Herodium near Bethlehem. And, in Jerusalem itself, archaeology has revealed soaring terraces, staircases and viaducts where the walls abutted onto the terrace of the Temple. These monuments make a better candidate than Jerusalem's aqueduct for the architecture of the Rome painting.

The epoch of the siege and sacking of Jerusalem fits the date that has been suggested so far for the painting. And few cities would have been so famous in Rome in the last quarter of the first century: the conquest of Judaea was the achievement that legitimated the new dynasty of the emperor Vespasian and his son Titus, and the people of Jerusalem had participated in the colossal triumph that marked the victory. The spoils of the Temple were paraded through the streets of Rome, as depicted in the reliefs of the surviving commemorative Arch of Titus. Like the Colosseum, Titus's Baths and the ironically named Temple of Peace, all of which also commemorated the glories of the conquest of Judaea, the arch was in the same part of the city as the painting. The tragedy of the siege, with its terrible suffering, would have been well known.

But there are problems: the building on the left in the painting is certainly a theatre, and, although we know that Herodian Jerusalem had one, it is surprising to see it given so much prominence. The building on the right is a massive temple, and it is just possible to imagine that the configuration of walls, prominent towers, theatre and temple were an attempt at a topographic rendering of Jerusalem at the time of the siege. But — and it's a very big but — the temple doesn't look architecturally much like Herod's Great Temple, about which we are quite well informed. And, above all, it seems to have a huge anthropomorphic statue of a divinity in its courtyard!

So the extent to which the painting is meant to represent Jerusalem, or actually does portray it, is still unclear. Altschuler may be right, and the building on the right is a public building other than the Temple, which was depicted elsewhere on the painting; or the painter may have been extremely ignorant, and only seeking to convey a rough evocation of Jerusalem. Or Altschuler's interpretation may be combined with the view I expressed in my earlier piece: that this is a capriccio, a fantasy city, but one into the creation of which important elements of the wonders of Herodian Jerusalem have been incorporated.