Pokémon Diamond and Pearl/Route 213

Events
Route 213 is the first route in the game requiring the use of the Waterfall HM. Cynthia will give it to you when you defeat Volkner. Head north on the route to reach a waterfall, and use Waterfall on it from a Pokémon to go up. Heal and save in the Pokémon Center, and leave to go east to the opening for Victory Road.