I parked at the Pavilion and took the Main Somerville Trailway (including a small loop via Nails Creek Trail).
The trail was mostly a wide service road and a bit rocky at times. There were a few rolling hills, but nothing very difficult.
I opted to take the Flag Lake Loop Trail around to where it rejoins the main trail. There were a lot of ducks and birds on the pond.
I took the Main Trail as it zig zagged to the small bridge at Yegua Creek. There was a guy fishing there at the creek. He had caught a fish that was about 10 inches long.
On my way back to Flag Pond, I decided to take the west route, but I got off course here because the map wasn't very accurate in portraying the service roads vs the trail. As a result, I walked out of the park, past a gas facility and onto some rancher's land before I realized I was off course. The park could do a better job here by posting better directional signs towards the trail as well as when you are leaving the park boundaries.
Once I got back on the right trail, which incidentally is right along the lake shore, everything went fine. The trails were in very good condition overall. I saw a few deer and some wild boars on this hike, but they were scared an quickly ran off to avoid me.
This trail is also frequented by equestrians, although I did not see any on this weekday.