In the gate between Nacrene City and Route 3, you can talk to the PKMN Breeder there and she'll offer to give you a Pokemon Egg. If you say Yes and have room in your party, you'll receive an egg that will eventually hatch into a Happiny.
On the actual route, there's a School Kid near the entrance that will fight you in a Rotation Battle. She uses a Skiploom L61, a Jumpluff L61, and a Bellossom L61. There's a Quick Ball right next to her, too.
Cross the bridge for now, but keep in mind there's some hidden stuff you can reach if you use Surf. Swing down through the grass on the other side of the bridge and fight the Fisherman there, who uses a Slowpoke L61, a Goldeen L61, and a Seaking L61. Right past him is a Zinc.
If you have a Pokemon that can Surf, now's your chance to use that to cross the water to the north. There's a small patch of land directly north that may seem empty, but it actually has a Hidden Grotto by it.
|Route 3 Hidden Grotto (West)|
|Bibarel Lv. 55-60
|Venonat Lv. 55-60
|Lombre Lv. 55-60
To the west of that is another patch of land. The Fisherman there is the ubiquitous Magikarp guy, having a team consisting of six Magikarp, all at level 58. Have fun with that. West of him is a hidden Ultra Ball in the blank patch of grass. Up the steps is a Full Restore to the right and a Calcium to the left. That's all there is, though, so head back on over to the bridge.
East of the bridge, the route continues, with a fence separating the dirt path from some thick grass. Inside of the thick grass is a School Kid that will battle you in a Triple Battle, so be ready for him. He uses a Xatu L61 (middle), Fearow L61 (left), and Natu L61 (right). Just past him is an excellent Big Nugget, which can be sold for $30,000 to the ore maniac in Icirrus City. Nice! To the north of him is also another Hidden Grotto.
|Route 3 Hidden Grotto (East)|
|Pachirisu Lv. 55-60
|Manectric Lv. 55-60
|Zebstrika Lv. 55-60
Anyway, go back onto the road and follow it north. You'll have to fight Backers, who use a Pachirisu L62 and an Emolga L62 in a Double Battle. Take them out, then head north until you find yet another branch in the path. Before you decide where to go, step into the grass and pick up the Ultra Ball.
To the east leads you to your destination, Striaton City, while heading over to the west takes you to an optional location, the Wellspring Cave. It's your decision which direction to go, though.
I'll start with the Wellspring Cave route, so head on over to the west and follow the path until you find a cave. That's the entrance to the Wellspring Cave. There's also a Lass who will fight you using her Vulpix L62 and a Flareon L62. There's also a Nugget hiding over by her.
Now, heading east from the fork in the road leads you over to some Twins. Don't worry, though, because they won't fight you. Up the steps is the Day Care Center, where you can drop off one or two of your Pokemon. It's also where you can breed a compatible male and female Pokemon. The house to the left of that is a nursery.
Talk to the Nursery Aide directly inside and she'll heal up your Pokemon. There's a Rare Candy for you to munch on in the top-right corner of the room, too. Outside, the Nursery Aide blocking the entrance to the playground will battle you, and she uses a Jigglypuff L61, a Purugly L61, and a Lickitung L61. There are three Preschoolers playing in the playground. The girl uses a Kirlia L61 and a Pikachu L61. The boy next to her uses a Beldum L61 and a Deino L61. Lastly, the boy on the slide uses a Riolu L61 and a Ledian L61. There's also a hidden Rare Candy in the sandbox.
Well, that's all there is to do here, so head further east along the road south of the Day Care Center until you reach Striaton City!