Here you will encounter lots of joggers, bikers, dog walkers, ducks, and Dallas beauty. You can see the lake (duh), the Dallas skyline, and glimpse the arboretum as well.
There always seems to be something cool happening, and if not, there's definitely always some solid natural scenery.
Play ping-pong, check out a book, and play some putt-putt. Not simultaneously. That would be difficult.
Why pick green space or city when you can have both? Main Street Garden Park is smack in the heart of Downtown.
Why limit yourself to ONE Downtown garden? Belo Garden features plenty of native trees, gardens, and a fountain plaza.