Location of the Frigidus River

[Lothia]

Ave Civitas,

I am doing research on the battle of Frigidus. I just found an article,
http://en.wikipedia.org/wiki/Claustra_Alpium_Iuliarum
that states:
Most importantly, the Battle of the Frigidus took place in 394 between Castra and Ad Pirum.

Both of these places are in Slovenia. Castra is inside the present-day town of Ajdovscina and Ad Pirum is up the valley (to the east) and central in the plateau halfway between Ajdovscina and present-day Ljubljana.

However, I cannot trace the flow of the Frigidus up that narrow valley nor can I confirm the route of the Roman Road that ran from Castra to Ad Pirum.

Anyone have more information?

Thanks,
Tom