Ered Luin, also known as the Blue Mountains, is a mountain range in Middle-earth, primarily featured in J.R.R. Tolkien's works. It stretches from the northern regions near Hollin to the southern areas close to Eriador. The mountains are known for their rich deposits of minerals and are home to various creatures, including dwarves and elves. The Ered Luin served as a significant location for the Dwarves of Durin's Folk and the Grey Elves. It played a crucial role in the history of Middle-earth, particularly during the events of The Hobbit and The Lord of the Rings. The mountains are characterized by their rugged terrain and scenic beauty.