Testaccio is the 20th rione of Rome, Italy, identified by the initials R. XX, deriving its name from Monte Testaccio. It is located within the Municipio I. Its coat of arms depicts an amphora, referencing to the broken vessels that Monte Testaccio is made of.
Sources
Text: introduction of the Wikipedia article Testaccio, under the CC BY-SA 4.0 licence (authors: article history). Facts: Wikidata (CC0). Coordinates: Wikidata, map background © OpenStreetMap contributors.