A distant shot of the Sawpit Dam with a good portion of Monrovia Canyon Park under all those trees.
You can barely make out the Nature Center at the far left side, middle of the photo.
The waterfall trailhead is behind the Nature Center and goes back into the canyon. The most popular trail in the park. Relatively easy at 3/4 of a mile (one way) and shady most of the way.
The road you see snaking along the right side of the dam leads to the Trask scout camp and to the Ben Overturff trailhead. The section of road visible in the photo is the paved section. It's steep and winding, far and away the worst part of the hike. It's also a private road so no parking on it or near the Ben Overturff trailhead. It turns into a dirt road at the scout camp and more or less parallels the Ben Overturff trail. I recommend walking up the dirt road to either the Twin Springs or Deer Park trailheads and hiking the trail back down.