Galicia & Upper Hungary, around the Tatras

The Tatras are really marvelous; they lift up right out of the plain, surrounded by a flat land.  They were formed millions of years ago as a sharp, staggering wrinkle caused by the collision of the African plate with the European ... with their sharp lifted peaks formed by the glacial period.  Go have a look.  Yet as spectacular as they are, they're just 26 miles long and 7 miles wide.  We could fit six of these ranges into the area of Long Island.

They're an untouched wilderness in the period, primarily inhabited by shepherds and hunters.  The forests today have all been cut out, but they'd still be there in the 17th century, all around the lower slopes.  The upper pastures were tended by a group called the Goral people.

The more populated regions to the north are peaceful and deeply hierarchical, with the peasants being largely serfs, often on the edge of starving.  The Polish nobility of the time ravaged their own land and peoples without restraint, supported by the Catholic Church.  It's a hard place to live, but a player party could likely walk through the region with little trouble, so long as they were generous with bribes, should they be questioned.  Two silver pieces per soldier is a good bribe, all given to the leader of course.