Giant Rock is a seven-story-high freestanding boulder covering over 5,800 square feet, believed to be the largest of its kind in North America. The site has long been considered sacred by Native American tribes, particularly the Serrano and Chemehuevi, who conducted spiritual ceremonies there. In the 1930s, eccentric prospector Frank Critzer built a subterranean home beneath the rock, which later exploded under mysterious circumstances during a police raid in 1942. In the 1950s, George Van Tassel, an aviation engineer and UFO contactee, hosted Interplanetary Spacecraft Conventions at the site and claimed to channel extraterrestrial messages beneath the boulder. Paranormal reports include, electromagnetic anomalies, and spiritual vortex effects, especially near the Integratron, a nearby dome built using plans allegedly received from aliens and inspired by Nikola Tesla. Witnesses also describe silent craft, light formations, and contact experiences, making Giant Rock a cornerstone of UFO lore.