Wait until the TV says "Lilycove dept store cleareance sale!" after that go to the roof of the Lilycove dept store and talk to the lady at the top she will sell bridges and other cool things.
well they are secret bases but you need to teach one of ur Pokemon secret power(tm43), and u can get it in slateport city at the open market!(In Pokemon Sapphire).
There are secret bases in Pokémon Ruby Sapphire and Emerald. In Diamond Pearl and Platinum, you have underground bases.
I would say the one on the way to de-activate the generator at new mauville near the cycling rode in Ruby, Sapphire, and Emerald.
In generation 3, the only games that include "secret bases" are Pokémon Ruby, Sapphire, and Emerald. The LeafGreen and FireRed, Kanto reboots, unfortunately did not include this particular feature.
Here is the easiest possible way there is no easier way than this, First you need to mix records with other ruby and sapphire and emerald games to get there secret bases and make sure the games have really strong Pokemon that your Pokemon can handle, mix records with the strong Pokemon in your party and in the other games party then mix records. Next find the other players secret bases with the Pokemon your training and have the Pokemon that your training hold a lucky egg then defeat the trainers in the secret bases and you will level up very quickly.
they are secret bases you need to teach a Pokemon secret power first to use them
of course
On the way to Fortree city.
Secret power can make secret bases for you find a tree or bush or indent in a wall then use secret power on it and inside is a base this is a place where you can decorate and customize your own place! Also if you mix records with other ruby and sapphire and emerald games you can battle other peoples secret bases! Secret power also can inflict opponents Pokemon with poison, flinch, parlyze, sleep, and can lower stats like speed.
Secret bases are hidden around hoenn its a hideout for you, all you have to do is find a big bush or a tree with vines or an indent in the wall and you use the TM secret power on it and a hole will appear or a vine inside is an area where you can use decorations to make your own secret hideout, if you mix records with friends they can battle you in your secret base and you can do the same if they did that.
its nothing like ruby and sapphire its in the PC again but only trades data not bases etc
NO NO NO NOO