1) Ancient Roman festival 
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...