The 5 is a trail that crosses the Northen slopes of Immitos from east to west or from west to east (depends from were you heading i guess) and passes nearby the characteristic antenna building of OTE at the last turn before the entrance of the infamous 10 trail.
Thus most of the riders that use it preffer to consider as a starting point this building.
From that building and exactry on the turn of the tarmak road, just dive into the easter entrance. You'll find yourself descending through a fine trail between large rocks and through steep steps. Minimoum loose stone bed, in comparisso to the same trail of the west slopes.
The trail crosses the dirtroad that circles the northen slopes of Immitos.
Better return from there, as we discovered that the trail, after the first crossing with the dirtroad, becomes a riverbed with hudge round slippery rocks. (if you ride that i'll buy you a beer!)