Lots of horses....
This hike is a good leg-stretcher, but not a great hike by itself. The entire hike is in a dense forest of primarily Douglas fir but also tanoak and bay trees. The summit of Firtop at 1,324' is covered in trees and doesn't have any views. This hike's biggest drawback is that its route sees heavy equestrian use. You know what that means, and it doesn't smell so bueno on a warm day. Apparently there is a horse ranch that takes paying customers out on the trails. The cowboy/girl guides get the horses going real fast for about 100 yards then slow everything down. It's actually quite amusing, and makes me glad that I walk.
The trailhead is large and can hold at least 50 cars, but there will probably be horse trailers and big trucks. The hike starts to the right of the vault toilets, and there's a sign with a crude map about 30 yards up the trail. The wide roadlike trail passes a large pond on the left that was formerly used by logging operations before reaching a 3-way junction. Go right onto the Stewart Trail which is a hard dirt road that routinely sees Park Service trucks.
There's a junction with the Greenpicker Trail about 1.25 miles in and another one with the Ridge Trail at 3 miles. Veer left at Greenpicker and right at Ridge to remain on the Stewart Trail as it gradually ascends to within 150' as the crow flies from the summit of Firtop. You're in the heavy tree cover that you've been in the entire hike, but there's a few small meadows just west of the summit that may have wildflowers. Go right on the Greenpicker Trail near the summit as it descends about 3 miles on a single track. There are some nice views north to Olema Valley and Barnabe Mountain about halfway down, but you're still mostly in a dense forest.
This hike would best be utilized as part of a big hike to either Glen Camp just west of Firtop or Wildcat Camp down at the coast or a great dayhike that went down to the coast and back.
Check out the Official Route.