This is a fairly grueling but fun ride that can be done in around two hours at a leisurely pace.
Start at the Ester Community Park just off the Parks Highway before Ester. Ride back out the Parks Highway for a mile or so to the intersection with Goldhill Road. Start up Goldhill and either go directly to Henderson or take any of several paths up the hill. Either way, you come to a powerline (the main Fairbanks-Healy intertie). It is about two-tenths of a mile up Henderson. At any rate, there are several trails going on up the hill perpendicular to this powerline. Take any of them and you wind up at the Ryan Lode Mine.
You can explore the mine or keep going either around it or through it to Henderson. You ride up Henderson for a bit (depending on where you come out on Henderson) to a road branching off to the left which immediately forks about 50 feet in. This road is immediately after the main mine entrance. Take it and then take the right fork. Follow this trail for about a half-mile or so until another trail branches off to the right, going uphill. This trail takes you up Ester Dome for about another mile and a half or so to where a powerline intersects it at a T intersection. This is the Alder Tube.
Turn right and push your bike up this hill (about three-tenths of a mile or so). When you get to the parking lot at the top, turn left and follow Ester Dome Road up to the top of the hill. Go past the last of the radio antennas and continue on down the double track. Follow it for about two miles. You will go past the Ester Mine Road (described in greater detail here) and just before you come to the turnaround point for the Equinox Marathon, there is a rough single track going down the hill to the left.
This trail drops down, levels off, drops down again, levels out and climbs a shallow saddle for about a half mile, and then intersects the Fireplug dog mushing trail. In the winter, you could take this trail all the way to Nenana if you were so inclined. However, since you will probably be riding this trail in the summer, turn left here and follow it all the way down to Quartz Road (NOTE: the final downhill on this trail is quite bumpy and rooty. Full suspension is a good thing to have here, and healthy brakes are a must!)
The trail comes out at the end of the little valley through which Ester Creek flows. From here it is about two miles of level riding on a gravel road all the way back to your car. The total distance is around 13 miles and can be done in under an hour and a half by a determined rider or group of riders.