In my alternate history, during the Islamic golden age (in this case, 9th century Arabia - present day Oman), my characters are building a series of glass towers.
They are like lighthouses traversing from present-day Muscat to Niswah; 6 towers, one every five miles (total 30 mile journey). For aesthetic purposes, they want to make them out of glass with minimal stone support.
I'd like the six towers to be glass, and about 10 stories high; imitation of Western lighthouses. The foundation is sandstone jebloon (or little rocky mountains). What will the requirements and limitations be? Where should stone supports be?
There are no issues with security, or storms, and the engineers have been given the best engineering literature from North Africa to the Levant and Arabia (imagine they have access to the sum of the Islamic renaissance, for this question).