Sorry I missed your email!
the nature center is the old building on the other side of the river from the fish ladder. Access the river frontage road from the montgomerey / table mountain traffic circle.(not sure if the road has a name - its the road that accesses the picnic sites and nature trail along the river) I usually park half way to all the way down the road. I haven't run other Lake O trails only because I have a pretty narrow time window in which I can run (while my kids are in gymnastics) - i'd rather spend it running than driving :-) -- and I don't know the area very well. I'm certainly open to other trails close to the downtown area!
This week running Lake O 4:15-6 on tues, also running Lake O thurs & fri (starting time TBD). Mon I may run in Bidwell unless I wimp out in the midday heat - if so I'll run Lake O trails mon eve.
Happy Trails!
Linda