I live in parks.
I wake up in the morning and weave through the narrow streets of my near medieval-density neighborhood, cross two lanes of (admittedly ornery) traffic and find my way down the lush greenery of the Greenway, through fountains and lawns for at least a third of my commute, then into urban fabric so dense it makes traffic
It's significant because it could make urban density more than palatable to the vast majority of people, reversing the wasteful cycle of sprawl and highway extension we are locked in.
The thing it's missing is contiguity: the ability to walk from a building directly into a park setting, to avoid almost entirely the damaging effects of particulate exhaust inhalation that will certainly surface in health care costs as generations age, dangers of traffic to children, and prevent the foolish hope that you are that very special person for whom the universe has reserved a parking spot directly in front of your destination.
This does exist in one quiet but enormously pregnant instance: the "corridor" park that runs