In my own strange way, I view loop hikes as the most efficient use of time, only because you don't need to backtrack on the same trail just to return to your starting point. Loop hikes cover the most ground and get you seeing more of the forest or grasslands or whatever you're traversing. I know this may not make any sense to those of you out there who see no problem walking the same old path—for your sake, I hope this doesn't translate into other areas of your life. Anyway, I digress.
I've always loved the Purisima Creek Redwoods in the Santa Cruz Mountains overlooking Half Moon Bay, but its lengthy trails made it difficult to string together a moderate loop hike in just one afternoon. The main trail itself is five miles out, which means five miles back to your car. And, I just don't want to walk 10 miles in an afternoon, I don't care how luscious the redwood forest is. If that makes me lazy, then so be it. For other lazy hikers, I've put together a 6.5 mile loop—even that is a little long for me, by about a mile or so—with some significant elevation gain in the first half of the hike (just to warn you):
Park at the end of Higgins Purisima Road, which starts at the southern terminus of Main Street in Half Moon Bay, at the fire station. This road will take you up and over a mountain...just keep following it until you reach the car park.
Start the hike on the main Purisima Creek Trail for about a mile until you reach a sharp right turn uphill on the Borden Hatch Trail. Here begins the 2.5-mile climb. When you see a turn off for the Bald Knob Trail, don't take it. I only mention it because that's where the Borden Hatch turns into the Grabtown Gulch Trail, which is all downhill. Take Grabtown until you reach Purisima Creek again. Take a left and you'll be about 1.5 miles from your car. For the most part, this loop is not very busy; mostly it'll be you, your hiking partner(s), a couple of mountain bikers, and a supremely gorgeous forest.