If you use the equatorial radius and the exact latitude of the Parthenon then the speed is
365.646 meters. But this is incorrect because the radius at different latitudes is different. Thus you either have to compute the exact radius at Parthenon's latitude or use a mean like the volumetric mean radius. In the later case the speed computes to:

u = 365.237 m/sec

Earth tropical orbit period = 365.242 days

If we use:

[www.starpathdemos.com]

and consideru = 365.242 m/sec

then the ideal latitude is 38.146 degrees

Marathon latitude = 38.15 degrees

running a year Marathon standing still...