Park at the Day Creek parking lot. The first section is the Glenwood Horse Trail (3004E) - Day Creek to Boblett's Gap Rd.
There are two fireroads that come into the top of the lot, the singletrack is below both of these to the right as you look uphill. This trail has some stout climbs and a couple really nice downhills towards the end. At mile 3.7 you'll peak at the top of the third large climb and enjoy a fast, fun singletrack descent with one stream crossing to the Bobblett's Gap Road. If it's been wet recently the edge of the fireroad can be very muddy, so check your speed right at the end.
Take the left onto Boblett's Gap Road and climb until reaching a fork in the road. You'll stay to the left and go through a US Forest Service gate onto a rougher fire road and continue to climb. This eventually takes you underneath a bridge at the Blue Ridge Parkway.
Continue down the other side for a right turn a mile later. You'll see a sign for Glenwood Horse Trail #3004B: Mineshaft Segment
and the trail turns sharply back up the hill. After the first steep punch (hike-a-bike for most), the trail will mellow out and turn into a sweet piece of singletrack. There are a couple small scattered rocky areas but this section is mostly smooth. Towards the end, it turns into an awesome downhill with some rocky sections, switchbacks, and even some flow. One of these large rocky areas has clean lines, but can be intimidating, especially in the fall when the leaves come down. This section soon ends at a parking lot off of Pico Road.
Follow Pico road to the left out of the lot and continue for two miles until it comes to a T. Go left here and you'll be on pavement for two miles followed by one mile of gravel. Turn left onto the fire road which is the Boblett's gap road you descended earlier before Mineshaft. Climb this back to the Blue Ridge Parkway, take the left before the bridge underpass and you'll climb up to the Boblett's Gap Overlook picnic area. Go right (south) on the parkway for a few miles.
At mile marker 96, the trailhead for Spec Mines Trail
will be on your right. Spec Mines is a blast of a downhill - fast and tight sections and some loose rocky sections. You'll cross a large water bar and end at a gravel road.
Take this gravel road to the left and follow it to a four-way intersection and another left onto the Black Horse Gap Road. Climb this back up the Parkway and go right onto the Parkway again. Follow the Parkway south until you reach the Great Valley Overlook on your right. Directly across from the overlook there is a footpath to access Dody Ridge Access Trail. This short section to exit the parkway is NOT bike legal. WALK your bike for ~200 yards and then continue to the top of the short ridge.
Or continue west on the BRP to Salt Pond Road, which connects to the Quarry Road and the Glenwood Horse Trail (3004E) - Dody Ridge Trail
The Dody Ridge Access Trail climbs for a bit and then drops down the hill to the left. This is a steep chute with lots of loose rocks and some tight turns. Take the first left you come to and watch out for a large (~3ft) drop off. There is a ride-around option on the right.
This connects into the section of Glenwood Horse Trail (3004E) - Dody Ridge Trail
. The trail becomes an open, rocky ridgetop before bending left and dropping to cross a drainage in a loose, rocky, fun descent. Just past the first creek crossing, there is a Y intersection, stay left to continue descending to the road. Turn left to descend the road back to the Day Creek parking lot, ~1 mile down there is a washed out bridge with a ride-around to the right.