This was the general idea that I was going for:
http://www.pbs.org/wgbh/nova/lostempire ... ngram.html
http://member.fcc.net/workgroup5/pages/ ... n/9894.htm
It seems like they are pretty well protected from directly above with just the roof. I think they may have hung skins down on the sides for additional protection. They would probably be in trouble if they couldn't see a little bit of what was going on around them. Not sure. Any historians out there?