The northern stream definitely went thru Austia. As a matter of fact the name 'Celt' is a derivation of Salt, as these people settled for a while in Salzburg (salt-city), Austria.
There were various salt mines around Salzburg (salt city) and they furnished salt to the Roman Empire using CELTIC slave labor.
The really big salt mine was at Hallstadt, not far away, a fascinating place to visit. Aside from some dating problems, this is a decent brief article on Hallstadt. Click on my FR LostTRibe Profile below for more...