green corridors, eco parks, ecological parks, linear parks, green spines....

hi easa

is anyone aware of what cities have green corridors in them, or of any recent schemes which were about trying to create new green corridors in cities, especially more built up ones.
someone was mentioning a national geographic article about using old rail tracks as a new city park, i have been unable to trace this scheme, i think it was new york?

im looking at a scheme to make a new 18km long circular park through dublin city, which will incorporate the existing 2 canals of the city, europes largest city park; phoenix park and the botanic gardens
another side to it would be to attempt to get the cities soon to be built metro to travel underground the green corridor. ive called the scheme the "botanic spine" but im finding it very hard to come accross information
www.dublin.ie

so perhaps you might be able to help
thanks
dunk

above image from a proposal for such a scheme in chicago in the US
www.emporis.com