I've run games in every edition of Shadowrun and they've all been set in Seattle. I have never, in all that time, done anything more than mention the Ork Underground in passing. Perhaps this is a failure of imagination on my part, but I've always had a hard time picturing what the Ork Underground is like.
Recently I've done a bit of research online and found out how the RL historical Seattle Underground was created. I now have a slightly firmer foundation for my speculation, but I'd like to tap into the Dumpshock creativity to add to the description.
Here's a little summary from the wikipedia article on the Underground:
In brief, the Seattle Underground was created by building retaining walls along the edges of the old streets and filling the space in between with rubble from the fire-destroyed buildings. For some time the sidewalk area was not yet covered over and pedestrian traffic still used the (up to six meters) lower sidewalk level, having to cross by climbing ladders at intersections. Eventually the sidewalks were covered over, with small glass skylights installed in the sidewalks to let light down into the now-covered areas still being used for commerce until being closed in 1907 over fears of plague.
What I now picture for the Ork Underground is that most, if not all, of the original street level frontage has been recovered and refurbished. Most of the skylights would have been removed over the century worth of sidewalk replacement, but new ones could have been installed. That means 25 to 30 city blocks of narrow alleyways in a grid pattern mirroring the surface street pattern. My impression is that there were very few larger spaces kept in the underground, so if the orks and dwarves who first reclaimed the the Underground wanted to have more than a maze-like warren of tunnels that they'd have to do a fair amount of new excavation. This means tunneling into the areas of rubble fill under the streets and building new supports to hold up the streets themselves, or tunneling deeper. Either way, I don't picture a lot of wide open spaces. Perhaps the Goblin Market is one of the few.
Questions still to answer:
-The extent to which additional excavation has been done.
-The zoning; i.e. how is the Underground split between commercial, municipal, residential, and industrial spaces? Don't need anything super-specific, but a general idea would be nice. Does everyone live in the converted basements that line the alleys?
-How do these seemingly small spaces accommodate trolls?
-Has the Underground spread beyond the original 25 city blocks devastated by the fire of 1889?
-Seattle 2072 describes the Ork Underground as having a burgeoning population and a newly thriving economy. How does the Underground provide the services, like power, water, and sanitation, to support this expansion while still being described as operating under a "gentleman's agreement" with the Metroplex government? This "gentleman's agreement" implies the Ork Underground is not taxed or regulated by the Metroplex Gov't and in turn is not provided with any city services. The kind of private investment it would take to provide these utilities and services to enable a large population to survive, much less thrive economically, is totally at odds with past depictions of the economic and social status of the residents of the Underground. How do we explain it?
I think that'll do as a starting point. Please feel free to answer these questions and add more of your own. Hopefully we can get a brainstorming session going that will provide a resource for GMs looking to add detail to their descriptions of the Ork Underground.