It's a little northeast of Mossdeep City. You have to surf to get there.
Don't you mean Pacifidlog? Northeast of Mossdeep is Shoal Cave.
Well, technically, Shoal Cave is North-Northwest of Mossdeep, but that's being anal about it.
The Sky Pillar is east of Pacifilog (if you haven't already gotten there, dock there first; it'll save you the annoyance later). Surf to the right from town, but stay to the top of the route. A curved path will be there a slight ways in.
Shoot, my bad. I got mixed up.
Maddie Blaustein, 1960-2008
You will be missed.