Team Rocket Warehouse

After taking care of all that, it's time to face Team Rocket. Either fly or walk back to the Pokemon Center, and go south from there. After a while, you'll reach Rocket Warehouse. Go inside, and you'll see that familiar spin maze. Play around with the maze, and as you do, be sure to pick up important items such as TM36 - Sludge Bomb and Up-Grade. You want to reach the Scientist in the upper-right hand corner. Fight him, and he'll give you back the Sapphire. Be sure to press "A" against the box in this room for a Nest Ball. You're finally finished with the Rockets!

Now exit the Rocket Warehouse and surf west. Go up and pick up the PP Up. Now surf east a little to get to Memorial Pillar.