We should naturally expect that this sacred boundary would have its holiness secured or revived by an annual _lustratio_ like that of the farm and _pagus_; and so no doubt it was. But the memory of this survives only in the word _amburbium_, which, on the analogy of _ambarvalia_, must mean a rite of this processional kind. Luckily we have definite knowledge of the real _lustratio_ of a city in those ritualistic inscriptions of Iguvium which I have more than once referred to.[452] It is the _lustratio_ of the _arx_, the citadel of Iguvium, which we may guess to have been the original _oppidum_ or germ of the historical city. The details are complex, and show clear traces of priestly organisation; but the main features stand out unmistakably. A procession goes round the _arx_ (_ocris Fisia_), with the _suovetaurilia_--ox, sheep, and pig--as in the Latin _lustratio_; at each gate it stops, while sacrifice and prayer are offered on behalf of the citadel, the city, and the whole people of Iguvium. There were three gates, and each of them is the scene of sacrifice and prayer, because they are the weak points in the wall, and they need to be strengthened by annual religious operations; such at least is the most obvious explanation. Whether the Fratres Attiedii would have been able to explain it thus we may doubt; neither in the sacrificial ritual nor in the prayers, as recorded in the inscription, do we find any clear trace of a distinction between the sacred and the profane, or of the idea of a hostile spiritual world outside the sacred boundary. So far as we can judge from the prayers, the object is really a religious one, to implore the deities of the city to preserve it and all within it. The language of these prayers hardly differs from that in which a Christian Church of to-day asks for a blessing on a community.[453]