El Castillo del Diablo (English: The Devil's Castle) is a prominent set of rock formations in Grand Theft Auto: San Andreas, located in Bone County, San Andreas, northwest from Area 69 and southwest from Verdant Meadows.
Visible from miles around, the formations consist of mesas, buttes and one natural arch. Most of these geographical features, like the rest of Bone County, are likely to be inspired by Monument Valley, Utah.
El Castillo del Diablo sits immediately northwest of Area 69, and can easily be seen from Verdant Meadows, which is northeast of the rock formation, and the town of Las Payasadas, located further north. It overshadows the tiny ghost town of Las Brujas, the location of two missions in the game, namely "Interdiction" and "High Noon". The Snake Farm is located within the borders of El Castillo del Diablo to the northeast, close to Verdant Meadows. A mass grave can also be found at the foot of the centermost mesa in the area.
- A rock formation that looks like a penis can be seen from a cliff located on the end of the runway of Verdant Meadows. It has become affectionately known to fans as "Cock Rock".