Summer Glass

The city of Bridge is well known for its artistry, and perhaps no art is more famed from that marvelous place than that of its glassworkers. Indeed, most of the fine glass traded across Derathain comes from Bridge. With glasswork so common and so integral to the design of the city itself, it is perhaps unsurprising that leftover bits of glass are prevalent refuse in the city.
Rather than allowing such bits to go to waste, a tradition has grown to make use of the excess. At the start of each Summer a few days are set aside where glassworkers and vendors throughout the city come together to trade their odds and ends between them and with various artists and craftsmen. For the week after the trading marvelous mosaics, suncatchers, and other crafts are churned out by creatives across the city. Children are invited to observe and learn the skills of the glassworkers and many begin their apprenticeships during this time. 
Traders from Derath City and other major cities and settlements flock to Bridge to see what clever and unique works of art are produced during the Summer Glass festival. This has led to an ever-lengthening period of celebration, trade, and entertainment surrounding the festival. Food vendors and traders set up temporary stalls on either side of the canyon and performers, bards, and traveling theater troupes build small stages. Indeed, thanks to the fame of the event some artists make more during the week (or so) of Summer Glass than they will the entire rest of the year.
Officially the city only recognizes the one week of trade and craft, but they are always welcoming to the increased traffic and trade, and so what began as a small tradition of trading spare glass and using it to make things of beauty has grown into a celebratory event known across the continent.