Pytheas, after completing his survey of Great…
325 BCE
Pytheas, after completing his survey of Great Britain, travels to the shallows on the continental North Sea coast.
He may also have visited an island which was a source of amber.
According to The Natural History by Pliny the Elder: “Pytheas says that the Gutones, a people of Germany, inhabit the shores of an estuary of the Ocean called Mentonomon, their territory extending a distance of six thousand stadia; that, at one day's sail from this territory, is the Isle of Abalus, upon the shores of which, amber is thrown up by the waves in spring, it being an excretion of the sea in a concrete form; as, also, that the inhabitants use this amber by way of fuel, and sell it to their neighbors, the Teutones.”
The island could have been Helgoland, Zealand in the Baltic Sea or even the shores of Bay of Gdansk, Sambia and or Curonian Lagoon which were historically the richest sources of amber in the North Europe (Pliny's Gutones might have been Germanic Goths or Balt Galindians).
Pytheas may have returned the way he came; or by land, following the Rhine and Rhône rivers.