First. Invisible line splitting cities.

I've been inspired by Greenwich Prime Meridian Line. Line represents the Prime Meridian of the World - Longitude 0º.Every place on Earth is measured in terms of its distance east or west from this line. The line itself divides the eastern and western hemispheres of the Earth - just as the Equator divides the northern and southern hemispheres. I underlined word represents- line is imaginary in a sense that it is invisible (apart of laser line indicating it at night) and also, that position of the line was chosen randomly, by agreement of governments, so it would be advantageous for most. It means such an influental line was man-made.

In 1884 the Prime Meridian was defined by the position of the large “Transit Circle” telescope in the Observatory’s Meridian Building.

As the earth’s crust is moving very slightly all the time the exact position of the Prime Meridian is now moving very slightly too, but the original reference for the prime meridian of the world remains the Airy Transit Circle in the Royal Observatory, even if the exact location of the line may move to either side.

 http://www.nmm.ac.uk/explore/astronomy-and-time/astronomy-facts/history/the-prime-meridian-at-greenwich 

It's a classic photo opportunity: have your photo taken standing on the Prime Meridian Line at Greenwich. Head for The Royal Observatory and in the courtyard is a metal strip where you stand over the line and can be in the the eastern and western hemispheres at the same time.

But what if there was a physical wall dividing earth into two- east and west? Creating two worlds, new cities. What places, buildings line would it cross? How socially it would change city perspective? How physically you would move around the space?

In terms of curiousity, how things that we are aware of  would change if they would exist in reality and would become tangable?
Sense of the world- would perception change if you'd see it in reality?

     Gordon Matta Clark: 1974 Splitting, Exterior (in 6 parts)

James Corner + Alex S. MacLean - Taking Measures Across The American Landscape (1996)
‘As a creative practice, mapping precipitates its most productive effects through a finding that is also a founding; its agency lies in neither reproduction nor imposition but rather in uncovering realities previously unseen or unimagined, even across seemingly exhausted grounds. Thus mapping unfolds potential, it re-makes territory over and over again, each time with new and diverse consequences.’
James Corner - The Agency of Mapping: Speculation, Critique and Invention (1999)