Hoenn Route 120. Everything about this single route just screamed adventure to me as a kid: The rain ending, the giant puddles (which you could see your reflection in), the Kecleon on the bridge, the tall grass, the fact you could actually hear the cries of wild Pokémon, and of course, the music.
https://m.youtube.com/watch?v=Xzec20s-FlU&feature=youtu.be 