The west side of the Rocca di Angera has been used since Roman times as a quarry for Angera Stone. This is a sedimentary rock, a dolomite, already employed for building 2,000 years ago, e.g. in the Roman theatre in Milan. Its use increased notably from 1200 onwards; in the 18th century the quarry was officially closed because it threatened the stability of the Borromeo castle above. Barges moored along the lakeside next to the quarry to load up with stone; according to tradition there was a tavern at this point.