Only accessible on Irvine Ranch Conservancy Wilderness Access Days (it may or may not be open for use on these days). Visit the park's website for additional information.
Limestone Ridge is a hard alternative to Limestone Canyon Road in order to reach the Sinks. The desert-like ridge follows busy Santiago Canyon Road for a while, with unobstructed views of Saddleback Mountain and Limestone Canyon. Technical-minded riders may or may not appreciate this trail - short up and down segments (some steep with small stones), a narrow track, a few sharp switchbacks, thorny plants and a lot of small/medium sized loose stones are all just waiting for you to slip. A few short segments of this trail may require you to hike-a-bike depending on your skill level. The trail ends at the to the East Sinks viewing platform.