A mountain range beyond the desert outside ShiKahr on Vulcan, towards which the seven-year-old Spock set out alone to prove himself.
The L-langon Mountains are a range on Vulcan featured in the Animated Series episode Yesteryear.
In Spock's childhood he slipped out of his parents' home at night and headed for the mountains to test himself in the desert ahead of his formal kahs-wan trial. His pet sehlat I-Chaya followed him and was mortally wounded defending him from a le-matya.
When a change in history erases Spock, he goes back through the Guardian of Forever and, posing as a cousin named Selek, follows the boy into the foothills. He saves his younger self, and the child chooses to let I-Chaya die peacefully, a decision that sets him on the Vulcan path.