Stuff to do with my niece.

Any suggestions of how to spend about a half a day with my niece? She's 12 now and we've always been really close. I've taken her to a bunch of different places and I'm starting to run out of ideas. I try to make sure we never do the same thing twice.

We've hit up all the major attractions and some of the lesser ones - the bio-luminescent waves from last year, the tide pools, flower fields, torrey pines etc...

What else is there to do with a kid her age? I'm thinking of hitting up some hiking trails with her, but I'm not quite sure what's the most age appropriate.

Bonus points for North County options, but not a requirement.