I've plugged the Alps with Forts since RTW. The allow me to gather a militia army from Milan/Genoa/Bologna/Venice, which by about Turn 50 can raise at least a 3/4 stack to resist the enemy and protect those valuable cities, often my economic heartland. Also useful between Spain/France, and in parts of the Holy Land. Don't really have any purpose in the larger, flatter regions such as the steppes and north Africa though, except maybe at some river crossings.
Bookmarks