You can do a whole bunch of stuff here, first of all, there is a gym here, which you can battle to get your 3rd badge, in Emerald, you can rebattle this gym after you beat the elite four. You can also get your first bike or you can switch bikes here. There is also the game corner here... Which you can play to win special TMs. Plus, you can get the HM Rock Smash here.
Pokémart
| Mauville Mart | |
| Poké Ball |  200
|
| Great Ball | 600
|
| Super Potion | 700
|
| Antidote | 100
|
| Paralyz Heal | 200
|
| Awakening | 250
|
| X Speed | 350
|
| X Attack | 500
|
| X Defend | 550
|
| Guard Spec. | 700
|
| Dire Hit | 650
|
| X Accuracy | 950
|
Rydel's Cycles
Here you are given your very own bike! You are given the option of taking the Acro Bike and the Mach Bike. Your choice does not make a major difference, as you can exchange bikes at any time.
Mauville Game Corner
The Mauville Game corner has lots of TMs here. This Game Corner has Psychic, Flamethrower, Ice Beam and Thunderbolt! This is the only Game Corner in Pokémon Ruby and Sapphire. There is another Game Corner in Mossdeep City for Emerald users.
Mauville City Gym
This Gym specializes in Electric types. It is recommended that you bring a Rock Type Pokémon like Geodude which can be found in Granite Cave in Dewford Town.
Trainers
Kirk and Vivian can be fought individually or as a duel battle.
Beating Wattson wins you TM34, which is Shockwave.
This is for emerald version. Ruby/ Sapphire may be different.