Fractal used is Mixpinski from Vectron pack N°3, perfect for hard surface / buildings look with no limit for the scale.
Smaller changes to 4D rotations helped to break the symmetry at high iteration level.
The "Cross" that we used as ground for the city is located deep inside in the complexity of the 3D fractal, the challenge was to be able to create a mesh from any given position and zoom level.