The urban flattened group is for photos of urban architecture that seem to flatten all of the three-dimensional elements onto the two dimensional picture plane.
(Basically, photos of the sides of buildings that are shot straight-on so that the horizontal and vertical lines match those of the photo edges)
Please see the example thread or look through the pool if you’d like some clarification.
There are other groups for walls, textures, abstract architecture, street scenes, etc – please do not submit these to this group.