Post top tier code

Can be yours or not, I just want to see something good.

There is two tables that form a circular database =) it's mostly key values with some minimal extra info. So you have a list of edges accessed by the edge id, which just tells you the node id's for that edge, and the length of the edge. And you have a list of nodes that tell you which edge id's connect to that node, and the y,x coord of the node..
So if you're at (2,2) on the map above, the spatial index will tell you you are on edge id 2. Then if you look in the edge table, it tells you the next nodes are node id 1 & 2, and the length of the edge is 7..