This is a series of puzzle caches based upon the UCI World Tour. Each puzzle builds on the next and they will get increasingly more challenging as you progress through the series. The puzzles will lead to a trail of caches along official cycle routes and therefore are best done by bike. The caches are small and will not contain swaps but could cope with a small TB or geocoin.
Somewhere on the route of the 2015 Clásica de San Sebastián is a junction with several road signs. It is a junction the peleton went through more than once. One sign tells you that you are entering a place called XXXXX XXXXXXXX. Some signs tell you how far it is to Leso (ABBm). One sign has a name that sounds like a number followed by some roman numerals. Convert these roman numerals into a decimal to get CD. Pull the other Juan. Other signs give the number of one of the roads that goes through the junction, which is the GI-EFFB.
Subtract A from the Northing for stage 18.
Subtract (D-C)(E+F)B from the Westing for stage 18.
You can validate your puzzle solution with certitude.