Pinwheel Forest (Outer)
Right near the exit from the forest, you'll be able to head south into the grass or north on over to Nacrene City. Unless you're in a hurry, you might as well check out the southern part, as there are a few items and Pokemon you can run into there, not to mention Trainers.
The first Trainer you'll have to fight moving south is a School Kid. She uses an Oddish L60, a Tangela L60, and a Bellossom L60. Before you proceed much further south, head east of the School Kid to walk behind the fence. That leads you over to a Full Heal.
Head south of the School Kid and you'll find a Battle Girl, although she won't battle you. Walk on over to the east to find a Protein sitting by the trees. Keep going south from the Battle Girl and you'll eventually find a huge puddle of water with some thick grass over to the west. The Ace Trainer in there uses a Furret L63, a Braviary L63, and a Seismitoad L63. North of him is a Nugget while south of him is an HP Up. There's also a hidden Max Elixir in the giant puddle of water.
East of the puddle of water is another Ace Trainer. She uses a Linoone L63, a Mandibuzz L63, and a Toxicroak L63. Keep going east and up the steps to fight a Black Belt. He's got a Tyrogue L61, a Scrafty L61, and a Makuhita L61. Additionally, there's a Battle Girl nearby who uses a Tyrogue L61, a Machop L61, and a Poliwrath L61. There's a valuable PP Max right between them, too, as well as a Hidden Grotto off in the northeast corner.
|Pinwheel Forest (Outer) Hidden Grotto|
|Hariyama Lv. 55-60
|Bagon Lv. 55-60
|Medicham Lv. 55-60
|Poliwhirl Lv. 55-60
On top of that, the large rock you see in the middle of this little area can be chipped away by a Fighting-type Pokemon of yours once per day. If you have one in your party, you'll be able to break part of the rock off and receive a Star Piece, which you can sell for some money. It's not too shabby doing this each day to raise some funds, particularly if you sell the Star Pieces to the ore maniac in Icirrus City.
Head down the northern flight of stairs until you see a ledge you can jump down. Before jumping down, though, pick up the hidden Fighting Gem right at the edge of the ledge. Now you can jump down it and return to the School Kid at the beginning of the area.
From the School Kid, head north this time and fight the second School Kid running around. He uses a Venonat L60, a Yanma L60, and a Venomoth L60. Keep heading past him and you'll arrive in Nacrene City. However, as soon as you enter, walk behind the fence and return in the outer part of the Pinwheel Forest to find a hidden Ultra Ball.