Most people think that the ordon sanctuary is not accessible but only the arena on the right hand side is non accessible.
(edited pic from mmo champ)
At the yellow dot you will see Netural birds called "Highwind Albatross" attack one ONCE it will come and pick you up and fly you around the map when you get to the red x attack the bird till it dies and it will drop you at the back door then just head to the 7 and loot your chest it is possible to avoid all mobs with little effort. (The 2 big guys dont agro if you stay in the middle of them even while looting the chest)
you will prolly die from the fall but the spirit is up on the other side of the sanctuary and you can still run back (run back dead dont wait for rez and dont enter the sanctuary anywhere except where the red x is).
The birds do have other flight paths around the map and you can use them to get to some other unreachable chests try them out but if you dont catch one from the yellow dot it may not be the same flight path as the one described.
NOTE: No gliding or slowfall is needed for this method.
EDIT: i did this method on 6 level 90s including those in shit quest greens no problem.
EDIT 2:fixed img link didnt notice the pending approval thing