From 355 to Damascus is a great bike ride. You meet up with the paved portion of the Magruder trail on the far end. Nice remote(ish) scenery. As stated below the trail is closed to bikes west of 355, but you can pick it up again at Clopper lake and make a GREAT route via Clopper - Brink - Seneca Ridge (New MORE trail) - Schaeffer farms & back. Too bad there isn't a bike option so you could go from Damascus - Schaeffer farms & back. As a side note, with a little stint of road riding (from Black Rock Mill to 28 is closed, again, to bikes) you can hook up to the Seneca Bluffs trail and make it all the way to the Potomac!
Edit - Clarity
Did the 355- Brink Rd section.... nature in its truest form. Deer, rabbits and even a tortoise. Great time. One caution... at the Brink Rd entry point, there are two trails leading into the woods.... please do not follow the one to the right(near the river) ... a thick batch of poison ivy variant (these were not vines... just tall plants with flat leaves). Couldn't stop until I was in the thick of it.
What's with the shady looking building with a diesel generator and five (5) huge antennas near Watkins Mill Rd ? Anyone know ....
Walked this trail yesterday on an incredibly warm and nice day for mid-March! It was my first time there. I entered the trail from the 355 side and followed the "blue dot" trail. It wasn't that challenging, moderate ups and downs, as well as "ankle twisters" to watch out for as someone else who reviewed this pointed out. Saw lots of wildlife, and other hikers (people on bikes, with dogs, with kids, joggers). The trail was really dry but some places may be prone to getting muddy due to it's location next to the creek. I took 2 photos which I posted in the pictures section.