Editing Architecture (section)

===Window sizes===
For an architectural stone mullion:

4–6 inches wide — elegant, relatively fine
6–8 inches — substantial and probably most appropriate for your buildings
8–12 inches — massive, fortress/temple appearance

I'd favour 6 inches for ordinary architectural mullions and 8 inches for imposing Priestess buildings.

Example: a large arched window

Say you have an arched window 4 ft wide × 7 ft high.

You could divide the lower rectangular portion into three bays, approximately:

1 ft 2 in wide each, separated by 6-inch mullions.

Then subdivide each bay vertically with lead cames into panes around:

12 in × 20 in

The arched section above can use progressively smaller panes following the curve.

This gives you a window that looks large and impressive from outside, while no individual piece of glass is particularly large.

A useful rule for your Altierra designs

I'd establish this as part of the world's architectural convention:

No ordinary sheet of window glass exceeds approximately 18 inches in its longest dimension.

Exceptional temple glass might reach 24–30 inches, but would be expensive and prestigious.

That would also make large arched windows visually distinctive. The arch isn't a single expanse of glass; it's a framework containing perhaps 20, 30 or even 50 individual panes.