Before the arrival of humans, much of northeastern Europe was covered by primeval forests that stretched for thousands of kilometers across the European plains. Today, they have almost entirely disappeared with only a few patches of old growth trees standing in the most remote corners of the Carpathians and other mountainous areas. The Bialowieza Forest, spanning the border between Poland and Belarus, is an exception.

Covering just over 1,500 square kilometers, the Bialowieza Forest represents the last remaining primeval forest in lowland Europe. It is home to giant spruce trees, oaks and ash trees, and more than 20,000 animal species, including Europe's heaviest land animal, the European bison, also known as wisent, that was nearly hunted to extinction in the early 20th century.

Photo credit: Marc Veraart/Flickr