How do you get inside of the safari zone emerald?

First, you must go to Lilycove City. Then go left all the way until you reach the grass. Go up, left down, and then left up all the way again. You will see stairs. Go up the stairs then go left, and there will be two girls. Run past them, go up the other flight of stairs, and you will see the entrance, and you can go through.

Before performing this, an Acro bike is recommended, so you can get to the secret area. It is obtainable in Mauville City. If you want to get extremely rare Pokemon like Gligar or Stantler, you must defeat the Elite Four so the area that is under construction will be open.

Happy catching! I hope you succeed in catching really rare Pokemon!

You will also need a Mach bike to get to some of the areas in the Safari zone so if you want to explore all of it you will need to go in more than once.