That is, was it constucted by them like the iters?
Or is it just like the Silk Road, the name for the camel and wagon path of merchants, created by the traffic rather than specifically constructed.
It was more like the Silk Road. There was no Via Polonia or any similar road constructed by the Romans from the Adriatic to the Baltic.
There is an outline of its path (and the areas affected by its presence) at
http://www.bernsteinstrasse.net/eng/europaeische_bernsteinstrasse_eng.htm