A park I've always admired is Hong Kong park. I really like the way it's landscaped, with flowerbeds and lawns and some lovely old trees. There's a small river flowing through it, with ducks and waterfowl and water lilies floating on the surface. In the rainy season, you can hear the frogs croaking. There's an aviary with exotic birds flying freely under a net canopy. My ideal park would have all of these.
Also, I'd have plenty of things for people to do in my ideal park. For children, there would be a swing park with a climbing frame, a slide, some swings and a seesaw. For elderly people, there'd be tables with chessboards or maybe a bowling green. And a café or snack bar is essential!