Victoria lines - Mosta/Burmarrad Mystery Cache

An unusal mystery - the coordinates are given but you need to work out the hint from the riddle!

Now here is an unusual one !
Extracting the cache will not require moving rocks.
Early birds will have an FTF Coin!
Don't go before you break the riddle
That hides in these lines
Having a flashlight is useful
Reason is not that it's dark
Enough now, go find the cache!
Else you'll just sit there all day :p
Victoria lines is what the little wall in front of you is part of.
One can plan this as a way-point to walk from one side to the other of these lines.
Lines which start from Madliena and end in Bahrija
Traversing the whole island!
So even if you don't manage, there is still a bit of history in this place.

IMPORTANT: PLEASE REPORT ANY DAMAGE OF CACHE CONTAINER IMMEDIATELY SO WE CAN PERFORM REQUIRED MAINTENANCE!