The US Geological Survey awesomely allows you to download some of their incredible collection of cartography. This particular map is an 1897 rendition of Portland, which I combined with a digital scan of my hands. I was testing out opacity levels, & overlay techniques (I'm still very much an illustrator novice).
I was able to build a few more interesting pieces, but I think I'll keep those to myself for now... best to retain some mystery.