Power Plant

The Power Plant can be reached by surfing from the north part Route 10.  You can fly to the Pokemon Center on Route 10 to save some walking time.  Zapdos and the Electirizer item can be found inside the Power Plant.  You will begin a quest and once you complete it you will receive the Electirizer and Zapdos will spawn.  (Interact with objects, mainly on the wall, to complete the quest faster.)

You can also evolve certain Pokemon that require the Magnetic Field by leveling them up inside the Power Plant, such as Magneton to Magnezone.