While I was doing my research for my term paper (my question is: How did the proponents of garden cities believe that their proposal would solve problems such as overcrowding and poverty? Were they right? And if not, why?) I discovered that there are actually very few cases of pure garden cities, and none that were realized in the manner that Ebenezer Howard hoped that they would be. I’m doing my essay based on a few of the cities that were described in Peter Hall’s chapter on garden cities: Letchworth (the closest realization to a pure garden city), and Praunheim, Romerstadt, and Nordwestadt (attempts at a garden city in Germany). It turns out that most of the cities that had influences from the garden city movement would actually be considered to be satellite cities.
Where garden cities are surrounded by a large and permanent green belt, satellite cities are separated from the city by only a narrow green belt, or even just a park. Howard envisioned the city to be self-sufficient and self-governing, but citizens of the satellite city are quite dependent on the giant city for jobs and most other necessities, besides immediate and basic shopping needs. An example of a local satellite city in Canada would be Abbotsford, which is a satellite of Vancouver.
The fact that there are no actual realizations of the garden city (with all of its initial elements) shows that the garden city was extremely difficult, if not impossible to create to Howard’s original standards, and repeated attempts have suggested that the true garden city (to Howard at any rate) is likely unrealizable.
It’s interesting that you were looking at examples of Garden City experiments in Germany, as I discovered later during my own research for my term paper that Gottfried Feder, an early member of the Nazi Party, and the man largely responsible for drawing Hitler to the party, had actually published Die Neue Stadt in 1939, which was his attempt at a Nazi Garden City. While I had considered comparing his ideas against the designs of Albert Speer, I had to abandon this idea. Unfortunately, I wasn’t able to find much about it in English, but apparently, his ideas took into account the dependence that the inhabitants of the Garden City would have on a larger suburb, and would take into considerations the information gathered about these inhabitants and their needs. From this information, daily living and urban amenities would be planned accordingly. His Garden City was to have a population of about 20,000, which is more than the city of Yellowknife. I wasn’t able to find any specific examples of his ideas that were actually put into practice, there were apparently attempts in Japan. While i don’t exactly see what this has to do with Nazism, i’m sure that there’s much more to his ideas than this. Maybe he had some influence in the examples that you looked at?