Complex sentence: Crystal Springs Reservoir is an artificial lake located in the northern Santa Cruz Mountains of San Mateo County, California situated in the rift valley created by the San Andreas Fault just to the west of the cities of San Mateo and Hillsborough, and I-280.
Split into simpler sentences: Crystal Springs Reservoir is a reservoir located in the northern Santa Cruz Mountains of San Mateo County, California, United States. It lies in a rift valley created by the San Andreas Fault just to the west of the cities of San Mateo and Hillsborough, and I-280.