Inner Door. Mesa Verde.

One striking contrast between pre-industrial cultures and our own is evident in ancient ruins such as this.  All materials in this structure come from the surrounding land itself, and once it fell into disuse it quickly became simply another interesting variation in the local topography.  It also was built to last; no modern suburban American structure could be expected to last so well.  And yet other aspects of our culture will last all too long--those synthetic materials that are so ubiquitous in our constructions and in our everyday lives--the plastic bags and detritus that now litter the Earth, decomposing at a glacial pace, often leaving toxic compounds in their wake.