Tram lines radiate from the city to the park edges, so you can ride to the end of a line, ski or hike in a loop to the end of another line and ride home. That is a no-nonsense urban growth boundary. It forces development inward. There are no derelict blocks in Oslo. Space no longer useful for one purpose is snapped up for another.
Urban renewal goes on constantly everywhere.
There are few cars, because there's hardly any place to park and anyway most streets in the shopping district are pedestrian zones. Trams are cheap and frequent and go everywhere. The city is quiet, clean, friendly, attractive and economically thriving. There is a long list of things we could do. The accelerator part comes from widespread public subsidies to sprawl.