This medal looks to be made of brass or bronze. It looks like it was coated with some silver that has almost been worn off. All I could find about RIVA was that there was a battle there
Regarding the tower:
On the square surrounded by 14th century porticos are Palazzo Pretorio from the 14th century and the Apponale Tower built in 1220 and raised in 1555. The 34 m tower, built to defend the town, had salt and grain stores, storerooms, and exchange banks at its foot. It was used as a prison, then as an observation post during World War I. Above it stands the emblem of this city on lake Garda, emblem called "l'anzolim de la tor".
Source: http://www.lagodigardamagazine.com/riva-del-garda-lake.aspx