On your bike wherigo geoart is located near swan reach, the series is forever growing and will take you over a day if you do every wherigo properly.
The cache is NOT at the posted coordinates. Trust us.
In order to find this Reverse Cache you need to download a Wherigo cartridge made by -Waldmeister-
It is located here.
After starting it you will have to type in these three numbers when asked:
513268
752448
386009
Every time you ask it, the cartridge will tell you your distance from the cache, but not the direction.
Based on this information you should eventually be able to deduce the final location.
Once you get within about 20 metres from the cache, the cartridge will give you exact coordinates.