Also, Swansea Castle in Wales is right smack in the City Center: http://www.castlewales.com/swansea.html And Pueblo Grande here in Phoenix is surrounded by highways, the light rail, the old stockyards, and many industrial parks: http://www.pueblogrande.org/ And my favorite, though they're not exactly "ruins", is Gas Works Park in Seattle: http://www.seattle.gov/parks/park_detail.asp?ID=293
