What is a glen?

A glen is a narrow valley, especially one with steep sides covered in trees and undergrowth. It is a type of landform that is often found in Scotland, Ireland, and other areas of the British Isles. Glens are formed by the erosion of the underlying rock by water or ice over thousands of years. They are typically characterized by steep slopes, rocky outcrops, and a winding stream that flows through the bottom of the valley. Glens are often associated with Celtic folklore, as they are thought to be the dwelling places of fairies, or "wee folk."