I find this playground to be successful because of it singular structure-- thus making kids play on one thing together, and also having a creative and endearing appearance that any kid of any group would want to play on.
This playground works because of it's closed in one structure as well. It leads kids to be in one area all together and would lead them to communicate with eachother to move throughout the structure.
This is a playground structure that relying on motion through the contribution of many children. The structure wouldn't work or be fun to a kid without other kids being involved.
This is successful because of it's soft texture which would lead kids of all different aged to interact with each other.