Mirkwood

Beorn's parting advice to the travelers in The Hobbit is simple: do not stray from the path. The warning concerns Mirkwood, the vast forest that bars the eastward road, a dim sea of trees so wide that going around it means hundreds of miles and going through it means days of walking in green gloom. Its air is heavy, its squirrels are black, strange eyes gleam after dark, and an enchanted stream crosses the way, carrying sleep to any who touch its water. Wood-elves hold halls in the forest's north, a merry but wary folk who keep to themselves, and darker things are rumored in its southern reaches, where a shadowy power has its seat. Of all the perils between Bilbo Baggins and the Lonely Mountain, the crossing of Mirkwood is the one the company's advisers dread most.