Walkthrough
North of Route 17 is Route 16, the same that connects back to Celadon City. Much like Route 18, Route 16 doesn't have all that many Wild Pokemon and Trainers found within it. However, there is yet another Snorlax sleeping in the middle of the path, the same you will go into battle with when using the Pokeflute. From Celadon City, simply head east until you reach Saffron City. (If you took Routes 12-15 from Fuchsia City and are coming from Lavender Town, head west until you reach Saffron City.)
Interactable Pokemon
Snorlax (Pokeflute): Level 34
Wild Pokemon
Grasses:
Doduo (25%): Levels 31-36
Pidgey (20%): Levels 31-36
Pidgeotto (20%): Levels 31-36
Rattata (15%): Levels 31-36
Raticate (15%): Levels 31-36
Dodrio (5%): Levels 31-36
Grass - Special Spawns:
Chansey: Levels 31-36
Sky:
Pidgey (60%): Levels 3-56
Pidgeotto (35%): Levels 3-56
Pidegot (5%): Levels 3-56
Sky - Special Spawns:
Dragonite: Levels 3-56
Charizard: Levels 3-56
Articuno: Levels 3-56
Zapdos: Levels 3-56
Moltres: Levels 3-56
Trainers
Punk Guy Lao: Level 36 Onix, Level 36 Muk
Punk Guy Hideo: Level 36 Arbok, Level 36 Fearow
Roughneck Koji: Level 36 Raticate, Level 36 Rhyhorn, Level 36 Koffing
Obtainable Items
PP Up: Northern Grasses (Requires Chop Down)
TM14: From Girl In Northern House (Requires Chop Down)
Poke Balls: Defeat Punk Guy Lao
Poke Balls: Defeat Punk Guy Hideo
Poke Balls: Defeat Roughneck Koji
Awakening: Hidden Near Gate Beyond Snorlax
Post Game
Walkthrough
After defeating the Elite Four and starting the Master Trainers Challenge, you will find a couple of Master Trainers on Route 16. In total, there will be three Master Trainers to defeat.
Trainers
Bird Keeper Howie (Master Trainer): Level 70 Pidgeotto
Scientist Elton (Master Trainer): Level 75 Electrode
Youngster Cid (Master Trainer): Level 70 Lickitung