Cerulean Cave...
The faint sound of water from the ceiling of the dark, dangerous cave dripping on the cold, hard and sparkly surface is heard, the gentle sound of water flowing through the cave and the sound of powerful wild Pokémon walking around evident as well. But you're not here for them, you're here for the Genetic Pokémon, Mewtwo.
You climb up ladders, down ladders, solving puzzles, redoing them, tedious stuff, yeah. You find many treasures, stardust, golden nuggets, and many pretty rainbow-y crystals. But you can't seem to find Number 150, Mewtwo.
Finally, you see it, standing upon an elevated, rocky platform.. Is Mewtwo. Water surrounding the platform, you manage to get on it, Mewtwo sees you, its purple eyes glowing faintly with aggression as it sees you...