According to Lesley Adkins and Roy A. Adkins in their Handbook to life in Ancient Rome, "The Amburbium was a movable festival that appears to have been held sometime in February to purify the city of Rome. It seems to have involved a procession around the city, accompanied by prayers and sacrifices."
Amble Around the Urbs
Higgledy-Piggledy Urbs septicollis, or
Rome as we know it in
English these days,
Yearly was purified
Ambulatorily:
Walking around it and
Praying it stays.