The Forest Road or Elf-path was a means of crossing the forest of Mirkwood.
The path was wrought by the Elves in the Third Age of the Wood-land realm probably when Sauron occupied Dol Guldur and the forest became filled with evil things. Being the safest route through northern Mirkwood, Gandalf chose this way for Bilbo and Dwarves to take to the other side during their quest to Lonely Mountain. It may have survived into the Fourth Age.
Portrayal in adaptations
Before he left, the wizard Gandalf warned Bilbo Baggins and Thorin and Company to take the path, as it was the safest route through Mirkwood to the Lonely Mountain. However, Nori accidentally leads the company off the path, causing them to look for the path again.
Thorin was captured by these Elves, while the remaining company, with the exception of Bilbo, were snared by Giant Spiders. Bilbo rescued them with the help of his magic ring, but they were soon captured by the angry Elves and imprisoned by their king. With the aid of the ring, Bilbo eluded the Dwarves' captors. Weeks later, he found a way to free them: by stealing the keys from the guard when he and the Butler Galion, drank their supply of wine. Soon after they were freed, the Company fled in barrels and floated on the river that ran along with the Elf-path.
However, a small battle ensued as the Company made their escape.