In the 3D world it started small, simply laying out a block grid with a repeating bump map texture to help break up the forms. This was in 3ds Max with mental ray (I later moved to Vray 3).
These were placed on a flat site just so I could figure out what I could get away with. All that's required is for this simple block to be rotated or mirrored and large areas of a sci-fi city can be quickly created without it looking too dull. Every so often the replicated surface does need to be broken up so this when a large chasm or building is modelled. At this stage I began to look at 'hero buildings' - key bits of architecture that would break up the standard grid.
Next, I started on the lighting and also tried to use the z-depth pass to generate some atmospheric perspective. Already the scene is taking shape but it seems very 'flat'. The lighting was helping to break things up but the architecture could be more adventurous.
This is where I switched from mental ray to Vray - I seriously love Vray, this was the first time I had used it. Anyway, here I am adding architectural chasms and starting to fracture my initial grid.
The entire scene is lit with just one light - an HDRI sky from vizpark. The sky was also constructed from their hi-res sky images. It really surprised me that I could adequately light a scene using just one HDRI dome setup - no complaints though, keep it simple!
As far as UV mapping goes, all the simple replicating architecture bits were easily handled with a UVW box map. The 'hero buildings' all needed to be unwrapped and individually textured. Here's an example of a tileable texture (diffuse and bump channels) followed by a uv-unwrapped 'hero building'.
Some statistics: This was a pretty big project to undertake - it probably took 130 hours spread over 8 months - that's about 4 or 5 hours a week. The poly count is really low at just 1 million - although if I include the Vray proxies it goes up to 5.5 million. My PC really struggled so the scene had to be split into 3 parts, foreground, background and the tower - the background and tower were XREF'd into the scene to help viewport performance The final render is 10k high which looks pretty cool when printed at A1.
Update: Babel got into the Asian CG magazine INCG which is pretty cool! I was interviewed about the making of progress over 6 pages.