Sentinel Rock
Sentinel Rock is a granitic peak in Yosemite National Park, California, United States. It towers over Yosemite Valley, opposite Yosemite Falls. Sentinel Rock lies  northwest of Sentinel Dome.

How it was formed

Sentinel Rock formed when masses of rock split off Yosemite Valley's south-side cliff, along steep joints trending nearly east-west. This formed the near-vertical north face of Sentinel Rock.

Climbing
The most famous climbing route is the Steck-Salathé route, which is rated a  A0.

Climber Derek Hersey died while attempting to free solo climb Sentinel Rock in 1993.