Horsh Ehden is a mountainous ecosystem on the northern Mount Lebanon chain, located 3.5km north of Ehden and 100km from the capital Beirut. It ranges in altitude from 1300m to 1950m and covers an area of 1000ha (10km2) of which 350ha are forested. It was declared a Nature Reserve in 1992 based on its unique biodiversity and its almost untouched natural beauty, which changes from season to season. It is usually covered in snow from December to April.

Horsh Ehden extends over four valleys, and is home to mammals such as the wolf, the wildcat, birds, butterflies and most of the tree species naturally found in Lebanon: more than 35 different species of evergreens. The Reserve represents the natural southern limit of the fir tree (Abies cilicica). Stands of cedars are bordered by a mixed forest, of pine, wild plum and pear. 1,058 plant species of which about 200 are regarded as rare and 78 are regarded as medicinal plants are found here. This is the last remaining forest for the indigenous wild apple of Lebanon.

Local citizens initially resisted the idea of a reserve. They had traditionally hunted and harvested the forest and used it to hold their livestock.

There are a number of water sources in the reserve, the most important of which are Ain al Baq, Nabaa Jouiit and Ain al Baiada.