The Amburbium ("City Circuit", from ambire, "to go around" + urb-, "city"; plural amburbia) was an ancient Roman festival for purifying the city; that is, a lustration (lustratio urbis). It took the form of a procession, perhaps along the old Servian Wall, though the length of 10 kilometers would seem impractical to circumambulate. If it was a distinct festival held annually, the most likely month is February, but no date is recorded and the ritual may have been performed as a "crisis rite" when needed.