Short answers, pulled from the story.
The oldest trade in amber started from Sicily. Archaeologist Heinrich Schliemann discovered Sicilian amber beads at Mycenae, proving early southern European connections existed before the Bronze Age decline around 2000 BC.
Baltic amber gradually replaced Sicilian sources throughout the Iberian Peninsula from around 1000 BC. New evidence comes from various archaeological and geological locations on the Iberian Peninsula showing this shift after the Bronze Age period.
A main route ran south from the Baltic coast which is modern Lithuania today through Poland and the land of the Boii to Aquileia by the Gulf of Venice. Roman military fortifications were constructed along this path to protect merchants from Germanic raids during Roman times.
An amber deposit found in Partynice near Wrocław dates from the 1st century BC and is the world's largest archaeological find of amber. This massive collection currently resides in the Archaeological Museum in Wrocław.
The unofficial set of tourist sites stretches along a route from Gdańsk, Poland to Pärnu, Estonia called the Amber Road. Notable sites include the Amber museum in Gdańsk and the Kaliningrad Regional Amber Museum.