http://img519.imageshack.us/img519/6565/groundlevelendofyear1.pngNote: I dug out those extra tunnels, and built the wall but everything else on the map was there before. Its not even that huge of a deal, I always knew you could have multiple types of sites stacked together like this, ever since you had species conquering different types of sites...it just never occured to me to do anything with it in fortress mode.
Note the two ruined human houses, one stuck into the mountain, the other on the southern portion. The other human houses were pretty normal, except a few near the south had furrowed sand atop their floors, which all seems to be gone now.
The major challenge was just trying to figure out how I'd defend this sprawling settlement from a siege. The wall was a bit of a cop out, an easy, non-dwarven solution. But it was the best that occured to me.
TO ISGC: It was always there, but I couldn't tell it was a ruin without having been to it. I had no way of knowing whether or not it was inhabited from the Fortress mode map screen. Even if I did know it was a ruin, I wouldn't have known it was anything other then just a few empty human buildings. The thing that interests me is that its a mostly-intact ruin resulting from multiple civilizations inhabiting it.
Edit: Urist has posted while I'm typing. It looked like a crown for me on my screen, but I use a custom tileset so I'm not how that all translates out. I don't use DF without a tileset.