The first is Veppers' involvement. Veppers holds the position of "prime executive" of the Veprine Corporation. Given his arrogance and ideology that the self-made man is king, it is possible that the Veprine corporation is named after himself. What the corporation does however isn't cut and dry as throughout the book, Banks makes mention of the resources Veppers has at his disposal, and it appears that the Veprine corporation's interests include laboratory work, cybernetics, starship engineering, artificial intelligence and, oddly, tourism. Essentially Veprine is one of these can-do-anything conglomerates. Veppers is also so well-connected politically that it is possible the Veprine corporation has international clout. Chapter 19 makes mention that Veppers has numerous commercial interests in Iobe City such as ownership of the city's grandest hotel. So in a sense his business has influenced the evolution of the city. The existence of a private hotel room cut into the rock on the top two floors, as well as a tunnel to a secret hanger, make it seem unlikely that the hotel was bought out by Veprine, upgraded and remodeled. This sort of engineering is best done during construction unless Veppers went through the trouble of buying out one of the wallside hotels, made it the best hotel in the city and built his secrets later. This seems too coincidental to be likely.
That brings us to the technology and level of wealth of the city itself. Fair enough that there are a few buildings hanging from the ceiling, but the suspended ballroom is one of the more iconic examples outsiders would see of Iobe engineering. This structure is a premier social gathering spot hanging under the largest cavern opening by cables from the ceiling and possessing an iris-shutter roof in the primary dance hall. So whoever commissioned it undoutably had a lot of money and Iobe's builder community would need some heavy-duty innovation to manage it. The other thing that struck me was the mention of how fliers (sphere-like flying cars) are moved about the city. Banks mentions that pilot-operated flying vehicles are banned in the city due to various incidents of destroyed civil property, the compromise used for the flier Veppers and his party ride in is that flying vehicles are "tethered to tracks in the cavern roofs and controlled automatically." (Banks, pg.357). These tethers are mono-filament wires that are attached four to a craft. Another example of complex engineering as the caves would effectively cris-crossed on the roof by metal rails holding something between a hundred metres to over a kilometre down.
The third sign of technological capability is revealed when Banks explains what keeps the mercury simmering.
"the volcanic activity wasn't natural either; several hundred thousand years earlier - long before the Sichultians arrived on the scene to find a happily habitable but sentiently uninhabited planet - a hole had been drilled down through many tens of kilometres of rock to create a tiny magma chamber that heated the base of the cavern and so kept the mercury simmering." (Banks, 2012, pg.361)
When I first tried to understand the paragraph I was impressed but mistaken when reading that this chute was deep enough to perhaps reach the planet's mantle (real life drilling attempts have managed as deep as a little over 12km) but nothing like an artificial chamber underneath). But the paragraph also reveals something: The first colonists (or at least the discoverers) were Sichultians. But given the name (Iobe) compared to the only other non-Sichultian being in the chapter, Xingre, its possible that the name is Sichultian.
Page 367 reveals another engineering quality: An underground network of private roads, practically all of which lead to buildings or facilities owned by Veprine with some going outside the city. Infrastructure like this implies that Veprine essentially has an iron grip on the city's commerce, as an engineering project like this would require significant investment, planning permission and foresight. Perhaps also a little backroom dealing, given one earlier attempt of Veppers' to buy a Jhultian military vessel. But the prevalence of Veprine in Iobe would explain why the city authorities were the ones who organised a reception for him as Veppers would be a local benefactor. he might even have friends on the city council. But what this does suggest is that Iobe could be quite commercial, a tourist destination given the hotel, city bridges and ballroom and could be a prime source of business for Veprine.
Thus, I am imagining busy city lights, billboards, parks, shopping centres, theatres and hotel chains being a focus, architecturally though, as well as lights I did wonder if the city's architects could have been inspired by the caves in which they live in: Sligthly organic but maybe a glistening quality to the material.given there is a central river and wet karst caves become quite glistening. Maybe a slight Arabic vibe, as Veppers has been described wearing a billowing cloak at times, there is some interest in chromed windows and mutipurpose pillows that can float: Xingre and his lieutenant sit on ones that feature translators and Veppers' bed is a giant circular thing that features more floating pillows that can extend monofilament cables to hide what's going on inside the bed. Although that last one could simply be a disguised security feature.
One character under Veppers' care is also kept unconscious by a drug dispenser bulb on her neck disguised as an insect. An important note of this feature is that Veppers liked the visual touch (Banks, 2012, pg.367). Although he may have been primarily attracted to the innocuousness of a tranquiliser injector that looks like a tiny resting bug.