El Capitan in Yosemite National Park in 2287
"I'm doing this because I enjoy it. Not to mention the most important reason for climbing a mountain."
"And that is?"
"Because it's there."
"And that is?"
"Because it's there."
– James T. Kirk and Spock, 2287 (Star Trek V: The Final Frontier)
El Capitan was a geological formation in Yosemite National Park's High Sierras on Earth. Not precisely a mountain, it was actually a giant rock popular with rock climbers.
As a challenge to himself in 2287, James T. Kirk attempted to free climb El Capitan solo, without any safety equipment; an attempt which nearly resulted in his death. Fortunately, Spock saved the captain's life by using levitation boots to float high enough to catch a falling Kirk. (Star Trek V: The Final Frontier)