Venetians realized the value of their glassmakers, who were forced to be isolated on the Murano Islands in 1291 to prevent fire hazards from destroying Venetian neighborhoods and to reduce communication with other people. By the end of 1200s, glassmakers were not allowed to emigrate from the island so that their highly-sought-after talents could not bring fame and fortune to another region. In return, glassmakers were bestowed with "burgher" status--a much higher class than any other tradesman. The photo is from Google Maps, which has Copyright over the map data, but the users may "publicly display Content with proper attribution online, in video, and in print." Source: How Glass Changed the World by Rasmussen