This is part of the enclosed childrens play area that was built in 1996 by about 1800 volunteers to celebrate Bellevue's Bicentennial. It is much loved and draws many people to our neighborhood. We arrived about 2 years after it was built. At that point most of the trees were fairly young and there was not much shade. Now they are much larger and look great.
There's covered picnic areas close to the play area and many parents use them as discreet viewpoints to watch over their older children. Having said that it is fairly common to see the parents in the play area having as much fun as their children. The local teenagers enjoy the area as well :)