From the shelter at the top of Mount Falcon and Lair O' the Bear Loop
, after catching your breath, ride the Castle Trail
doubletrack until you see the Parmalee trail on your left. This trail is best ridden counter-clockwise. It's marked as difficult, but is mostly rideable by strong intermediate riders as well.
It's a fun singletrack reward after the big climb up, with a few rocky somewhat technical sections, and otherwise fast and flowy down with a moderate climb back up.
It ends at Meadow Trail
, which you can take back to Castle Trail