On everyone's local area bucket list should be the hike to the highest point in the Santa Monica Mountains - Sandstone Peak. That hike is about 3 miles round trip.
If you're looking to extend that hike, you can do the Mishe Mokwa Loop trail in reverse. Or you can explore several other peaks not far away - Inspiration Point and Tri Peaks. Hiking to Tri Peaks and back is about 6 miles round trip from the Sandstone Peak parking area.
Just north of the Sandstone Peak staircase/final ascent is a sign that indicates the trail to Tri Peaks. The trail is clearly marked and about 3/4 of a mile west you will come to the Inspiration Point spur trail. Do check it out as frankly I think the views towards the ocean are better here than at Sandstone Peak. Inspiration Point is 2,766 feet in elevation.
Another 3/4 mile or so of hiking gets you to Tri Peaks, which is 3,010 ft elevation, not too far behind Sandstone Peak. Tri Peaks is northeast of Inspiration Point and there are a number of signs that tell you you are getting close. The final sign before reaching Tri Peaks says you are .2 miles away. But after that, to my knowledge there is no official sign that says you have reached Tri Peaks. The final 1/2 mile spur trail to Tri Peaks is much more narrow than the main trail.
Personally when I went I was alone and in running shorts and t-shirt. Had I been wearing more appropriate hiking gear and long pants, I would have explored the peaks and caves a bit but without being properly equipped I opted to stay safe. But on the west side you can get some pretty sweet views of the Santa Monica Mountains towards Point Mugu and beyond.
Also, be careful to pay attention to the trail you came in from. There is no signage indicating the trail back, and the trail is not particularly clearly marked.