Other locations

Secret Base
Once purchased at Metchi Town (Far right) they can be accessed from any Pokemon Center downstairs behind the bookcase. (Interact with the back of the bookcase)

Grottoes
Hidden along routes, found by interacting with the trees

Grotto #1
Location: Near the end of Route 1; enter the cave and follow it to the Midna Garden. Grotto entrance is right next to the nurse.

Items and Pokemon available:
 * Great Ball
 * Dusk Ball
 * Super Potion
 * Full Heal
 * Stunky
 * Durant
 * Heatmor
 * Exeggcute

Grotto #2
Location: Route 3, directly north of the entrance to Metchi Town.

Items and Pokemon available:
 * Dusk Stone
 * Fire Stone
 * Hyper Potion
 * Pansage
 * Sawk
 * Throh
 * Charmander

Grotto #3
Location: Very beginning of Route 4.

Items and Pokemon available:
 * Great Ball
 * Quick Ball
 * Level Ball
 * Awakening
 * Panpour
 * Squirtle
 * Poliwhirl
 * Delta Sunkern

Grotto #4
Location: Crossroads; Use rock climb on the rocks at the bottom of the route and look immediately to your right.

Items and Pokemon available:
 * Full Restore
 * Max Potion
 * Revive
 * Leaf Stone
 * Pansear
 * Stunky
 * Dunsparce
 * Hawlucha