After you ride the Mamoswine through the deep snow of Mamoswine Road, you reach Anistar City.
When you walk into town, Sina walks up to you and says that someone in Anistar City knows about the Legendary Pokémon of Kalos. Sina gives you some Repeat Balls, which work best on pokémon that you have caught before.
The girl in front of the Pokémon Center can tell you a pokémon's memories. This is especially interesting if you read a traded pokémon's memory. You can choose any pokémon from your party or PC Box.
In the pokémon center, talk to Mr. Bonding to get Exp. Point Power.
Also in the Pokémon Center, talk to the girl in the black dress to get a TM. She will give you a different TM each day if you come at a different time of day.
Go east from the Pokémon Center and turn on the Dowsing Machine to find a hidden Super Repel to the right of the clothing boutique.
Go into the house to the right of the clothing boutique and talk to the guy to get TM10 Hidden Power. The move's type is different depending on the pokémon that learns it. Talk to the guy who gave you the TM and pick one of the pokémon in your party to learn the type that Hidden Power would have if that pokémon learned it. The move type can be different even if two pokémon with the same pokédex number learn it (for example, two Pikachus might each have a Hidden Power of a different move type).
The gatehouse to Route 18 is to the east, but construction workers are blocking it because the road was damaged by a bunch of Durants.
In the house north from the clothing boutique, talk to the old man to learn about the Legendary Pokémon of Kalos. If you are playing Pokémon X, he'll say that Xerneas went into hiding in the forest. If you are playing Pokémon Y, he'll say that Yveltal went into hiding in the mountains.
In the house north of where you learned about the legendary pokémon, there is a man who asks if you can lend him a pokémon level 5 or under to keep him company. The pokémon has to be in your party. You can always ask him to give the pokémon back. Even if you don't take the pokémon back, you will get it back eventually.
To the west, you find the Anistar sundial. There is a photo spot there as well. Turn on your Dowsing Machine to find a hidden Sun Stone to the right of the sundial's giant crystal.
After you go east from the sundial, keep going north from the Pokémon Center. There is café to the north. Use your dowsing Machine west of there to find a hidden Pretty Wing.
When you go east to the Anistar Gym, your neighbor runs up and starts a battle with you. The battle begins immediately. Your neighbor has a level 44 Meowstic, a level 44 Absol, a level 46 starter that is strong against your starter, and a level 44 evolved Eevee (Jolteon if you picked Chespin, Flareon if you picked Fennekin, and Vaporeon if you chose Froakie). Your neighbor heals up your pokémon after the battle.
After battling your neighbor, turn on your Dowsing Machine to find a hidden Escape Rope east of the gym.
After you're done exploring town, it's time to challenge the Anistar Gym.