I don't remember Poland ever extending to the White Sea in the north or Romania belonging to Poland in the south
That's why I was wondering about it. I'm also wondering with regards to the territory bordering what I believe is the Volga River, and including Crimea in the Black Sea.
All maps I've been able to find are of either before or after 1618 (when I've read Poland was at it's maximum extent).
And then on Wikipedia, found a map with caption "Rzeczpospolita in 1569; the Grand Duchy of Lithuania, having lost lands to the Russian state and to Lithuania's partner Poland, is much smaller than a hundred years earlier". So...how much larger was it a hundred years earlier and did that have a larger land-coverage than in 1618?