Amburbium
The Amburbium was a ritual for purifying the city. It involved a procession around the city, likely following the route of the Servian Wall. The exact date of the Amburbium is uncertain, but it was likely held in February.

Date: February
Observances: Procession around the city, sacrifice of a pig, sheep, and bull
The Amburbium can be difficult to distinguish from the Ambarvalia, another Roman ritual for purifying fields and rural areas. Both rituals involved similar procedures and sacrifices.
The Amburbium involved the sacrifice of a pig, a sheep, and a bull, known as a suovetaurilia. These animals were led around the city in a ritual circuit, a practice known as circuire. The purpose of the circuire was to purify the city and protect it from harm.
The Amburbium was likely an ancient ritual, dating back to the time of the early Roman kings. It was performed as needed, especially during times of crisis or danger. The ritual was believed to have the power to ward off evil spirits and ensure the well-being of the city.
