Madrid is supossed to have near of 70 km of biking lane around madrid:

http://www.munimadrid.es/portal/site/munimadrid/menuitem.8b2184148b70b0a...

Here you can find a map of the routes:

http://noway.es/files/greenLane.jpg
http://noway.es/files/PlanoAnilloVerdeCiclista.pdf

The route I present here is really small, just to try the Madrid green Ring

As I can see, it is not complete at all and you have to bike throught roads, get down the bike , etc ... Actually, until you reach the point 5, the real green lane doesn't start.