I did Athens marathon last year on its 2500 year anniverasy. I absolutely loved it, so much so that I am doing it again this year. It's a challenging course though, with about 18 miles uphill. The good news is that the last 6 miles are on a slight downslope. Organisation was impeccable. The finish in the marble Panathenaiko stadium can bring tears in your eyes. I think it's a must for maranthion runners!