Elysian Park, Los Angeles

I've hiked there a hundred times -- wonderfully varied views, some overlooking the downtown skyline, some completely enclosed in a nearly unbeleivable variety of trees.

The only downside is that the park is seldom used, and apparently the few who do feel shockingly comfortable dropping litter (sometimes only feet away from a trash can).

With a little support from the community this could be one of LA's greatest parks.