Long Pond Loop Trail is a 6.8 mile lightly trafficked loop trail located near Royalston, Massachusetts that features a lake and is rated as moderate. The trail offers a number of activity options and is accessible year-round. Dogs are also able to use this trail.
I use this trail often, and never get tired of it. It's also a great single track loop for mountain biking. When you get to the wooden bridges, and if you have the extra hour or so, take the hike to the top of Spirt Falls and back.
This is the best trail. I mostly ride on my Mountain Bike. It has everything from an old Revolutionary cart road to single track. You'll have to work on this trail. I'm often rewarded with seeing Heron,Deer, Moose and occasionally Bear. The trail is used by runners, hikers and Mountain Bikers. I often bring a fishing rod. The trail goes up one side of Long Pond and down the other. There are a few brooks along the way, too. Trail is 7.5 miles and I've ridden it in @ an hour. There are "Rock Gardens" and plenty of two board bridges so paying attention is rule #1.
There is a Triathlon in the Fall consisting of Kayak/Canoe, trail run around Tully Lake and Mountain Biking. Tri can be solo or team.