http://cdn.americansongwriter.com/wp-content/uploads/2012/09/owlcity_midsummer.jpg 

in that place. 

http://www.zeit.de/mobilitaet/2014-01/fs-crossrail-london-tunnel

2nd shot is awesome. 

http://i.imgur.com/8KMFhS7.jpg

from a serious of weird old pics which aren't really reference-y...

http://imgur.com/a/hZ3H2 

The circumstances behind each one. And playing spot the photoshop... 

 

http://cyber-hell.tumblr.com/

There might be some odd nsfw titty in there. I didn't look too closely. 

http://neuromaencer.tumblr.com/ 

Abandoned Places!

http://www.upsocl.com/cultura-y-entretencion/los-24-lugares-abandonados-mas-espectaculares-del-mundo/# 

The social media popup shit. 

z-axis baby
(youtube) 

Reminds me of a cross between one of the maps from CS but also seems a bit quakey.

http://www.deviantart.com/art/Casa-de-la-Julianeta-Portal-de-Molina-Albarracin-438984962 

Remind me a lot the small Italian city named Dolce Aqua (i.e http://en.wikipedia.org/wiki/File:Dolceacqua38_-_Panorama_del_paese_vecchio.jpg )
Basically, it is a medieval city with this kind of small streets with alots of interconnections...

Indeed very quakey :) 

There some decent night scenes on Google Maps/Earth and some interactive panos here:

http://www.albarracin.es/index.php?option=com_content&view=article&id=91&Itemid=497 

http://www.rjl-art.com/wild-concrete.php 

Make a base map like that. 

http://cghub.com/images/view/101293/

prey engine mods would suit quake pretty well. 

1997

markus klar 

to have atmospheric/lit control over fog like this in quake would be great too
[ http://www.thehundredth.com/wp-content/uploads/2010/08/2.jpg ]
[ http://www.cuded.com/wp-content/uploads/2012/07/Michal-Karcz_4600_600.jpg ]
[ http://31.media.tumblr.com/tumblr_lwx9emSqP81r90ca4o1_500.jpg ]
Or, any engine even?

(last two are Michael Karcz: http://karezoid.deviantart.com/gallery/) 

I've never seen any game engine treat fog for what it is, which is the interaction of light and airborne particles. Generally the best you can do is hand-author colored particle effects to simulate the reality, which is lighter, more opaque fog near light sources, and darker, more transparent fog in the shadows. 

NS2 does it I think (not sure if it's in the final game?) looks really moody.
http://youtu.be/PJMf7-HKw6A?t=1m3s 

Linear god rays are a special case, one you see a lot more often because they're based on an exploitation of render buffer blurring, IIRC. You've probably seen games where the god rays disappear when the sun goes off the edge of the screen. They're basically bloom with a radial blur instead of a gaussian.

Global fog comes from just masking in a color based on the depth buffer, and volumetric fog (like quake3 pits) also just masks in a color but based on the difference between two depth buffers (the front and back of the volume).

what metl and I are wishing for doesn't (yet) have a cheap implementation afaik. Raytracing will do it, but certainly not in real time, and piling up billboard particles slaughters you on fillrate.

paging lordhavoc. 

Well, you can just take the light entity position and use that as origin for the radial blur, so you don't need to blur bright on-screen pixels a la bloom to get the effect. It's just less cheap that way.

A cool compiler trick for Quake might be something that builds a shadow volume during build and does some texture magic to avoid hard edges. Could then simply (cough) be rendered as an additive mesh ingame. Of course it wouldn't be truly volumetric.

Another way I've seen them done is by billboards (taking slices along the length, bit like the shadow volume concept) and particle systems (point sprites scaling up in a cone like structure).

The scientific term for them is "crepuscular rays" by the way, if you feel like Googling.

Team Blur has also added them to their engine.
http://www.moddb.com/games/overdose/videos/overdose-vidoc-light-shafts#imagebox 

For that kind of things, search for the oldest parts of portuguese cities, for example Porto or Lisboa. Valenca do Minho provides very good environments too, but of another type.