Bush walks or other around Sydney

We may take advantage of the warm weather and head out for a hike/walk tomorrow. I'm wondering if anyone here might be able to suggest something new. Ideally it would be accessible by train. Usually the furthest we can travel is south to Otford or north to the Hawkesbury. The trips out west (mountains) take too long although we've been meaning to check out the Western Sydney Parklands. We'd be striking out from the inner city. Feel free to suggest anything and I'll let you know if we've been there.

We saw this giant dragonfly out the back of Heathcote about a couple of years ago (I think).