Glass is fragile. Glass golems are…very much not. They tend to serve as guardians or even spies. As with most golems, a party’s tendency to throw magic at a problem may not help them—and tossing around the usual fireballs could very well get them pulverized.
A reclusive wizard removes himself to the desert. After a storm it is his bait to seek out where lightning strikes have melted the sand into glass. He collects them to craft beautiful glass golems that guard his privacy and protect him from the many fire-flinging rivals he bested over the years, including an academy of evokers and twin half-red dragons.
Temples to war gods are typically fortress-like affairs with few windows besides arrow slits. The exception is the chapel at the War College of Edenburgh, whose roseate stained glass window is famous for its beauty. Less well known is the fact that the window can animate into a stained glass golem.
A glass golem rages across the bridges and byways of the canal city of Venua. Its master was slain by wererats and it has been maddened by its inability to follow them into the waterlogged sewers.
—Pathfinder Bestiary 2 138
I once saw glassblowing in Venice. Also Epcot Center. But Venice sounds way more impressive.