The cache is a black magnetic nano roughly 1.5cm cubed.
The given location is the 'Pentelis Avenue' suburban station on the yellow rail line. This line connects with the blue line at 'Doukissis Plakentias', or connects to the green line at 'Neratziotissa'.
This cache can be solved as part of;
HINT for the MoM: When the checker gives green light... you will find a clue for the next step of MoM.. 
Pyhr 1: Rira gubhtu yvsr vf abg n tnzr vs lbh jnag gb fbyir guvf chmmyr
lbh jvyy unir gb cynl gur Tnzr bs Yvsr.
Pyhr 2 : Jryy, yvfgra ohfgre
Lbh orggre fgneg gb zbir lbhe srrg
Gb gur ebpxvarfg, ebpx-fgrnql orng
Bs Znqarff...