The Blue trail is easily accessible, is great for hiking/biking, and has some great views across the lake.
Here are links to the official park site & to a trail map:
http://www.mercercountyparks.org/parks/mercer-county-park
http://www.jorba.org/sites/default/files/2010_SMART_trail_map_0.jpg
Just finished watching the 1st season of Marvel's Agents of Sheild and had the name Hydra in my head. For those that don't know, Hydra is the evil organization bent on world domination. Although, this is not an evil hide, I just had to use the name and it kinda fits.
Quick. Run back to the car and get your pen and tweezers, if you got them. You're gonna need them if you're continuing your MCPBT adventure.
ENJOY!