The current walls, which represent one of the most distinguished and best preserved examples of medieval military architecture in Europe, except the complex of Castel San Zeno and the parts of the walls to the east and west that are older, date back to the middle of the 14th century, when the Carraresi, lords of Padua, wanted to enlarge and strengthen this essential frontier fort of the Paduan state against the Verona of the Scaligeri, which dominated the nearby Legnago. The urban space intramoenia was expanded on that occasion, and the new enclosure was built with superimposed layers of bricks and stones (trachyte transported by water from the nearby Euganean hills). The fortified city is enclosed in an irregular quadrilateral of about 600x300 metres with an area of 24 hectares and a perimeter of about two kilometres.