Started at the Harvey Manning trail on a Sunday morning. There were only a few cars parked, with plenty of spaces. I started by checking out the "Million Dollar View" which overlooks Lake Sammamish and isn't bad, but maybe not a Million Dollars worth of view.
I headed south on the Tibbets Marsh trail, eventually reaching Clay Pit Road. I swung around the Mine Shaft, which is pretty impressive looking, to the East Fork and Shy Bear Trails to Shy Bear Pass. A trail run was going on, and at Shy Bear Pass was an aid station. After happily sharing their snacks, they showed me the route map and assured me the runers were well spaced out. This turned out to be true, as the whole day, I encountered only a dozen or so runners, and no more than a dozen non-runners.
Then it was off down the Deciever Trail to Long View Peak and its viewpoint, which is a bit too overgrown with trees to be considered a viewpoint. On to Doughty Falls, which is pretty, if a mere trickle. This section of trail was occasionally steep and muddy.
Then I wound back along the Shy Bear Trail to Fred's RR, Bypass, Cougar Pass, and Harvey Manning trails. I took the Lost Beagle Trail to a junction that showed on the map, but wasn't clearly marked with a sign. It is a small trail passing through a fence, which heads over to a picnic area in the old radar station. The trail crosses a small road beside a picnic table, and isn't clearly marked, but just past the picnic table are some old concrete steps that lead down to Radar Park, where there was a bathroom here which was closed for the season.
This brought me back to the trailhead, which had only a porta-potty.
The leaves are more off the trees than on them, but haven't yet started to decay, so the trail has a lovely paving of golden brown maple leaves.
In total, I walked about 7 miles, with almost a thousand feet of up and down elevation gain.

Link to the track on Gaia

https://www.gaiagps.com/datasummary/track/c53eb2eaba2b9089ff0fa61e70493704e2fc36ea/

Cougar Mountain Trails Map

Hike GPS data for GPS viewing

Per Garmin, 3.97 miles/433 vertical feet.

Parking: Almost no one at Sky Country parking lot this afternoon.  Lot has port-a-potty.

Trail: AMAZING; dry, leaf-scattered trails; yellow and orange leaves against a cloudless blue sky; swells of warm autumn air buffeting you as you climb.  You've got to come enjoy this before the weather turns. (On the hike map, ignore my adventure down one of the Clay Pit mine roads; there is nothing interesting down there.)

WTA Work: I must have just missed the WTA crew doing water mitigation work on Mine Shaft Trail; the excavated dirt was still damp.  The WTA has radically change the wet season hiking experience on Cougar Mountain.  Five years ago every trail was a puddle/stream strewn muddy wasteland.  Really, I just can't thank WTA enough for opening up these trails to winter hiking by people not wearing fishing waders.

Wildlife: Big gardener snake, birds chirping, frogs croaking.  Also, the trails are crazy with awesome mushrooms.  Look for Stropharia ambigua (shiny yellow caps fringed with a cottony veil remnant and PURPLE gills underneath) and Hypholoma fasciculare (densely packed yellowish mushrooms clustered on decomposing wood).

Caution: Blind corners and drivers disregarding traffic directionality create Sky Country parking lot hazards.  Every stretch of the figure-8-shaped lot is a one-way (see the attached picture).  Directionality is indicated with traffic signs and pavement arrows.  However, people frequently drive against the one-ways.  We’ve all disregarded parking lot traffic signs, but the lot has blind corners that are only safe when directionality is followed.  I have seen people charging excitedly into the parking lot and around blind corners with the confidence they have the right-of-way to the whole lane.  I have also seen people in a hurry to get home drive furiously around the same blind corners the wrong way.  At some point, people will collide.  So, do not be one of those people; recognize that, once you are in the parking lot, Mad Max rules apply and drive cautiously around every corner assuming someone could be hurtling against the one-way toward you.

This was my first time in years hiking on Cougar Mountain, and my first time ever in this section. I parked at the Newport Way Big Tree Ridge trail head where there was room for perhaps 3 more cars if they blocked the gate. Not sure if that would be permissible, but there were no signs indicating that it wasn't allowed. There was a large information sign with a map, and a covered tray containing maps of the park and its trails for the taking.

Started hiking at 11 AM. The well shaded trail starts off wide with a gentle slope upwards, and soon gets into dusty switchbacks as it climbs up the mountain. The trail surface ranges from dusty dirt to gravel, to dirt with gravel or small rocks. Overall, throughout the park the trails were in good to excellent condition - our tax dollars at work! In fact, with the exception of only three intersections, all of the trails were signed with distances to other connecting trails in the park.

Upon reaching Shangri-La Trail, the trail switched from hiker only to one where horses are permitted. The trail was as wide and as smooth as a gravel road, and was still very pleasant. No evidence of horses having been there in the past couple of weeks was found.

My lunch stop was at "Million Dollar View", aka The Pergola. Besides the picnic table in the pergola there are two other tables nearby. This area is also reachable by car, with a sizable parking lot nearby, and a Port-a-potty as well as a restroom in the nearby field.

When I arrived at the Pergola a bicyclist was using that table, so I used one of the others. He left soon afterwards, and I had the place to myself for about 20 minutes before a family walked over for their picnic.

Continuing onward to the west portion of Shangri-La Trail I found that this section was much more like a hiking trail than a road. Just before it reached the park border it intersected with Coyote Creek Trail, which is a wider trail at this point. Again, this trail is mostly shaded as it heads southward.

The cave holes along Cave Hole Trail are just a short distance from the intersection with Bypass Trail, so I went to see what it was all about. Imagine some deep depressions covered with foliage with fences and signs telling people to keep out and that's pretty much it.

Fred's Railroad Trail was another pleasant road-width and road-smooth trail. About midway down its length on the south side I saw the skeleton of an old multi-story tower off in the forest. I'm not sure what it had been used for, but it was probably left over from the WWII days.

The East Fork Trail was the first place I encountered some bugs as well as a small fallen tree across the trail. It also looks like this trail could get muddy in other seasons. Otherwise, the hike to the mine shaft was pretty uneventful. The mine shaft (formerly used as an air shaft for the coal mine) was covered by an immense rebar grate. A sturdy wooden bench put there by an Eagle Scout makes this a great place to stop and have a snack. An information board next to the trail described the coal mining activities as well as the purpose of the shaft.

Heading to Tibbetts Marsh Trail one is on the Clay Pit Road for a short distance. That road ends at the clay pit, where one can find another informational sign describing how the clay from the pit was used and why. The area is being reclaimed as parkland and nature is gradually taking it over.

Tibbetts Creek Trail travels along the edge of the steep ravine in which the creek runs. I didn't actually see or hear the creek; perhaps it has dried up at this time.

Returning to Shangri-La Trail I then headed over to No Name Trail, Surprise Creek Trail and, just for a change of pace, decided to try to take the Precipice Trail as it appeared on the map to rejoin Big Tree Ridge Trail. Well, the map is wrong. Instead, the trail ended up at the Harvey Manning Trail at Talus by a small park with some very nice playground equipment.

Looking at the County Park map revealed no way other than retracing my steps back up the mountain to take the other trail. Google Maps, however, showed a Precipice Bottom Trail that would take me where I wanted to go. So, off I went on the unsigned trail.

This trail was in quite good condition, with a number of small bridges and generally followed the contour line. However, the western section climbed up and up and up, finally reaching the Big Tree Ridge Trail at an unsigned intersection. The rest of the way down was anticlimactic, but I was happy to have brought a pair of walking sticks for the more slippery sections.

With all the stops for pictures, lunch and snacks I ended up at the car at 4 PM, having walked 9.8 miles with a little over 2000 feet elevation gain.

So far as traffic is concerned, I encountered about a dozen folks on the way up Big Tree Ridge Trail, including a couple walking their leashed cats and another couple shortly afterwards walking their unleashed dog. Other trails were either entirely devoid of people or had two or three other encounters. In general, it was pretty quiet considering this was a weekend in an urban area.

Due to the recent snow, the trails were often muddy, had large puddles, and even small amounts of flowing water across the path. There were a few downed trees; none that were particularly hard to overcome, but not suitable for some older people. 

The wildlife itself was quite beautiful; lots of mossy trees and we even saw a few chipmunks. I would remind people to keep their dogs leashed, as this isn't an off-leash trail area and several people we came across had their dogs running wild. This disturbs wildlife and can be unexpected for someone who may have chosen these hikes for their on-leash rule for whatever reason.

Even a simple place like Cougar Mountain can become a winter wonderland! We started at the Wilderness Peak Trailhead with the trail being pretty slick in the first half mile because of how well used the trail was, making it icy. On our way down the ice melted into slush. But if it refreezes at night, be careful. We and hiked up the Wilderness Cliffs Trail up Wilderness Peak. As we got away from the well-used parts of trail, the fresh powdery snow was pretty nice on the trail. Then from Shy Bear Pass we hiked Fred's RR and East Fork Trails to the big mine shaft and the clay pit. We hiked Cougar Pass and Anti-Aircraft Ridge Trails up to the viewpoint of Lake Sammamish at the Harvey Manning TH. We then followed the road from the parking lot up to the top of Anti-Aircraft Peak and hiked down the Lost Beagle and Coyote Creek Trails, then down the Cave Hole Trail and then to Coal Creek Falls. The waterfall and creek were amazing in the snow. We hiked back up Quarry Trail back up to Shy Bear Pass, and down Wilderness Creek to the TH. The more traveled sections of trail are icy of slushy and microspikes could be helpful. But the lesser used sections were great and easy to hike on.