Elephant Rock, the icon of the lower Merced river canyon, is home to some splitter cracks below, and amazing sport climbing above on Killer Pillar. Accessing the lower routes (not Killer Pillar) is possible only during low water (unless you rappel in from the top, which can be epic). There is an amazing swimming hole right on the hwy 140 below Elephant Rock.
From the Hwy 120/140 junction, go a little over 2 miles west on 140. Park on the left at a long, paved pullout by a stone wall (first parking past the Cookie), with a beautiful swimming hole below. Walk upstream to the top of the swimming hole, where a jumble of boulders allows you to cross the river. From here you angle mostly up, following a faint, cairned, trail that becomes more and more obvious the higher you go.