The city of Milan, Italy, has had three different systems of defending walls. The oldest, the Roman walls, were developed in two stages: the first in the Republican era and the second in the Imperial era. The second wall system was realized in the Middle Ages (12th century), after the destruction of the city by Frederick I Barbarossa. Finally, the latest wall system was built by the Spanish rulers in the 16th century. While very little remains of these walls, their structure is clearly reflected in the urbanistic layout of the city. In particular, modern Milan has two roughly circular rings of streets, namely the "Cerchia dei Navigli" and the "Cerchia dei Bastioni", which essentially correspond to the Medieval and Spanish walls, respectively. Note that a third ring of roads just beyond the Inner Ring Road (circonvallazione interna / "Cerchia dei Bastioni"), called the External Ring Road (circonvallazione esterna), does not follow any old city walls, but rather was part of the 1884 Beruto Plan for the city of Milan, created and named after a municipal engineer and public servant to the local city government.[1]