The two turtles are clues to your easier target. First turtle is pointing to NE the other to SE. Figure this out: direction of vaults aligned like stairway is usually North to South and vise versa, (smallest which is shallow to biggest deepest vault). Look for signs at NE and SE that those turtle are pointing and if you found those two signs are exactly aligned North to South then you got the vaults alignment. Your next task is to figure out the smallest one. Is it in the north or south? That is crucial to easy success, if you mistakenly dug the biggest vault then you may fail. Vaults buried like stairway are commonly 5 to 7 cache with 3 to 5 meters interval in depth.