Hill 394 used to be a look-out point for US Marines in this former Navy base. There are two dirt roads leading to the summit, one of which features one KILLER climb--almost 2 km at a 30-40 degree grade--but from the top it's one helluva ride down. The roads are seldom used since they're officially off limits to civilians. Singletracks could be a bit difficult to find since this section of the base is not exactly maintained on a regular basis. Trailheads tend to get hidden by bushes and bamboo.
How to get there:
Proceed to the Upper MAU in Subic Bay then take the road to the base hospital. Pass that then watch out for the dirt road on the left side. Park there and start biking or proceed to a clearing some 2 km up the dirt road and park there. This is where the first downhill section starts.
Watch out for monkeys and wild boars. Stay clear of them if you encounter them on the dirt roads.