Did the old abbeys have glass in their windows?
Well naturally occurring glass, like obsidian, has been used since the stone age. Glass making itself is believed to have first developed in Syria, Mesopotamia or Old Kingdom Egypt. Ancient cultures from South Asia to Italy (the Romans) have used glass. As to Abbeys, well Medieval Europe had some of the finest examples of stained glass windows, though few have survived to this day. Glass was generally expensive so only the rich could afford it. Wealthy Abbeys generally got wealthy because many people donated money or funds for improvements to them (in exchange the monks were expected to pray for them). So Abbeys would have had glass windows, and the wealthier ones would likely have had some extremely fine stained glass windows.
