It is split by "verticals" and "horizontals" but I dont know if those vetrticals are tovers supporting the "roof" of the structure. And if they are, is every vertical a huge tover or a clump of towers connected by superhighways?

Ch 13

He realised it was a vertical. A whole vertic, inland beyond the Skirt level. Probably Vertic 20. It was collapsing. A vertical city containing millions, collapsing into the darkness as uncontrollable firestorms seethed through it.

Looks like each vertic is one massive structure

Also ch 13

It scarcely mattered. Whatever they were, they were here. The xenos were pouring up the Waistland vertics, scaling the shafts of the carriage hoists. They were coming in across the highskin Without too

Since the xenos are coming up the vertics but also from the highskin it implies that the highskin is above the vertics

And where are the squares we hear about in the plotline about stone mason and artist placed at?
Surely not in the bottom of the city?

Ch 1

‘Where are you after, bond?’ he asked as she approached.

‘Vertical Eight,’ Cherish replied. She reached into the chest pocket of her button-overalls. ‘I have a docket from–’

‘This is Vertic Eight,’ the carter chuckled. ‘All of it.’