Cities are often compared with living organisms. They are born, grow, and sometimes even die.
One of the basic characteristic of any living being - the presence of the border between organism and the environment. It can be membrane, skin or bark... This analogy can be continued even further: sometimes this border transforms and we can spot the traces of the structure previously used to form the edge the organism already being immersed deep in the living creature.
And it just went into my head that the city borders can be likened to the trees' yearly circles...
I shot my pano right on such a spot, where the city border used to be long ago. A 37-kilometer long wall has been surrounded the old Moscow untill the middle of the 19th century, serving as the administrative border of the city, easying the police and customs control of the authorities over the people and goods flow. Now this structure is completely gone, but we still can spot on the map the circle-like pattern where this border lay.
Just for fun I've added some image labels using great application vrhotwires
from Bill Meikle
. Hope you like the effect.