Pokémon Red and Blue/Power Plant

'Head back through Cerulean City to Route #9. Go to the edge of the river in the northeast corner and use Surf to dive into the water. Paddle south until you reach land, then climb out and enter the Power Plant to search for Zapdos, one of the rarest Pokémon of all. Be warned that some of the items strewn across the floor are actually disguised Pokémon.'

The Plant
You don't have to beat the Power Plant to win the game, but the single level 50 at the end is incentive enough to make this short dungeon a must-visit before you challenge the Elite Four (and Red players won't want to miss their exclusive ). Another good reason is TM 25 which contains Electric's power technique, Thunder.

To get to the Power Plant, Fly to Cerulean City, then head east until you get to the river part of Route #9. Use Surf, and you'll find the plant with little trouble. A Pokémaniac waits outside the plant for any challenger with his and his. Beat him to earn 1500.

There's only one floor, but the enemies can be tiring. Use a Max Repel or bring a lot of Grass and Ground-type Pokémon. Dig is especially good, taking out just about anything in one hit. And remember, all that glitters is not gold... Most of the item balls that you come across in the Power Plant are actually Voltorbs. Only pick up the ones that are marked as items on the map! There's also a hidden Max Elixir in the "middle" rectangular room if you go into the dead end all the way around the boxes, and a hidden PP UP in the dead end two rooms before Zapdos.