Cork City Marathon '07.
If you are doing the Marathon next June, you might be interested in the following. I measured the route on an OS map and calculated roughly where the 10 km, Half Marathon and 20 mile mark will be.

a) The 10 km point should be near the entrance to the Jack Lynch tunnel.
b) The half Marathon point should be near the start of Centre Park Road, at the road junction at the back of Carey's
c) The 20 mile mark should be somewhere between where the Tennis Village used to be and the Ballincollig roundabout.

(Note! The points above are the approx locations. When I measured the course on a map, I got approx 40 kms instead of the approx 42 kms which it should be. Even allowing for errors in measuring off a map, an error of 2 kms seems to be a lot.)