In his alternate history science fiction art book Flodskörden, Simon Stålenhag lists three "Vertical Cities"[a] in Järvafältet: Hägerstalund, Eggeby and Berggården. Hägerstalund and Eggeby are - in our universe - still there. The former is a farm where you can find a Moroccan restaurant, Hägerstalunds Bibi House[b], and the latter is a public park[c] with theater, circuses and such.
But it was the third that stood out for me: Berggården. Never heard that name.
A bit of googling later I found a photo of the ruins[d], which clued me in to where it was. The painting Vertical Cities[e] also had clues - if you look at the towers you notice that the middle one is farthest away and between the other two. Plot the angles to Hägerstalund and Eggeby on a map with the viewpoint being somewhere northwest of Hägerstalund[f], and you've narrowed down the location fairly well.
Here are the remains of Berggården's feed table. The barn disappeared sometime between 1980 and 1981, and the residential building burned down in the mid-70's.