Behind the Philadelphia Museum of Art, behind the Rocky Statue, behind the Waterworks but before Boathouse Row is the Azalea Garden. I like to go here when I have exhausted all my other regular spots. The area is full of flowers in the spring but with all those azaleas come a lot of bees – so look out for those. The open grassy area is safely set back from Kelly Drive, has free and easy parking and is great for a picnic, mini soccer game or T-ball. It open yet cozy if that makes any sense.
If you want a view of the river just move your party across the parking lot and you can sit on the huge grassy spot right before the Waterworks starts. Just note that it will be a little mushy on that side if it rained the night before.