Lagour

The Flaming Mountain of Lagour is a mentioned landscape feature of Calormen.

Volcanic Activity
Mount Lagour may have been one of the only active volcanoes in the world of Narnia. It was likely similar to a cinder cone volcano in structure, and could have been continuously erupting. These eruptions could have lasted for centuries, hence the indication of prolonged volcanic activity in the mountain's description. Presumably the lava erupted out of the volcano from underground country of Bism.

Trivia
It is not known if the mountain was real or legendary. The description of the Flaming Mountain of Lagour is similar to the Biblical description of Mount Sinai: "Mount Sinai was covered with smoke, because the Lord descended on it in fire. The smoke billowed up from it like smoke from a furnace, and the whole mountain trembled violently." - Exodus 19:18, New International Version