In 1370 , he ordered the construction of the Trezzo Bridge , then the largest single - arch bridge in the world .
The following war against the Este of Modena and Ferrara raised again Papal enmity against the Milanese , now on the part of Gregory XI .
In 1370 , Gregory XI ordered the construction of the Trezzo Bridge , then the largest single - arch bridge in the world .
The following war against the Este of Modena and Ferrara raised again Papal enmity against the Milanese , now on the part of Gregory XI .