Specifically, anything that would promote the feeling of walking through a city at night. The kind of feeling one would get walking through Detroit at 2am in the winter, cold and desolate, surrounded by a man-made forest.

It may seem like splitting hairs, and I may be stretching here for a more specific ambience with a urban feel, but I would greatly appreciate any suggestions.

Less focus on the desolate forests and such.

Any metal "genre" will do, honestly.

I'll go with the most obvious, Perdition City of Ulver.

Lustmord, Northaunt, Nordvaggr- all pretty mechanic and ambent. Only the last two are really metal-affilated.

second "Perdition City" !!!!!!
if it hasn't to be "metal" mandatorily you may also like ANHEDONIA ( http://www.myspace.com/anhedoniacz ) and KAMMARHEIT ( http://www.cycliclaw.com/12thcycle.html ), maybe even some stuff of AIDAN BAKER and NADJA.
Oh - and try RIVERZ END, a russian ambient band who got their album for free download some time ago... (can't find the link right now, sorry)

Try "Monolith" and "Psychedelic Avenue" by Bardoseneticcube. The latter is a free online release, you can download it here - http://bsc.radionoise.ru/psya/

I would recommend 'Dead Cities' from The Future Sound Of London. One of the few electronic albums, that captures the bleak and gritty atmosphere from an industrialized city almost perfectly and transforms it into sound. It was also a huge influence for Ulver´s 'Perdition City'.

I was just going to recommend this. One of the few electronic albums I still listen to. Great atmosphere.

Are we perhaps getting a bit excited by the use of the wrd 'CITIES' in album/song titles here?

That said, try Sideliner- Crying Cities (ambient/electronic- NOT METAL AT ALL)....

Cities Last Broadcast is something you enjoy while walking through a city at night.
http://www.myspace.com/citieslastbroadcast
it is dark ambient with industrial influences and the idea behind this release was to give the impression of desolate places; like cities or industrial complexes.

Agreed. Quality suff for sure.

A bit more ritualistic but still cityscape/dark ambient is:

Endvra - Black Eden.

I know this isn't metal but if you're into industrial, VNV Nation's Empires album has the atmosphere you're looking for. It has a very "dark angel" feel to it (funny enough, that's the name of one of the songs on the album). Every time I listen to the album, I feel like I'm some lost, mournful spiritual being standing atop a skyscraper looking down over a vast, post-modern city while it's raining. If you've seen the movie Equilibrium, you'll know what I'm talking about (the album would've made a perfect soundtrack for it as well). Here are some songs from the album I think perfectly fit the mood:

Standing:
http://www.youtube.com/watch?v=Xk4gZEAmOLk

Darkangel:
http://www.youtube.com/watch?v=u3-IPG-XnaU

Arclight:
http://www.youtube.com/watch?v=NzxpvRni-74

Blut aus nord - Mort a little metal feeling and a very psichotic cityscape

i guess Bleak Emptiness from India is really nice.. the guy has some nice city/industrial soundscapes,
www.myspace.com/bleakemptiness ,
other than the songs up on there, you can ask him for his other stuff for free