kromer's works and other contemporary maps, such as those of gerardus mercator, show the commonwealth as mostly plains. the commonwealth's southeastern part, the kresy, was famous for its steppes. the carpathian mountains formed part of the southern border, with the tatra mountain chain the highest, and the baltic sea formed the commonwealth's northern border. as with most european countries at the time, the commonwealth had extensive forest cover, especially in the east. today, what remains of the białowieża forest constitutes the last largely intact primeval forest in europe.