New Mauville (Japanese: ニューキンセツNew Kinsetsu) is a power plant located underneath Mauville City in Hoenn. Due to its unique location, the complex can only be reached by Surfing from Route 110 east under the Seaside Cycling Road to a small island east of the overhead path.
It was originally intended to be an underground city, before it was found that it served as a habitat for wild Pokémon.
In Pokémon Ruby, Sapphire, and Emerald, Wattson stands at the intersection of Route 110 and Route 118 after the player earns the Balance Badge. He requests that the player shut down the generator in New Mauville as a safety precaution. To allow the player access to the underground plant, Wattson gives the player the Basement Key, which opens the door to New Mauville permanently. Wattson will remain in the center of Mauville City until the player returns, giving the player TM24 (Thunderbolt) as a reward after they shut off the generator.
In Pokémon Omega Ruby and Alpha Sapphire, after defeating or capturing GroudonOR/KyogreAS, Wattson stands in front of the Square Tower in the outdoor area on 1F of Mauville City, where he will tell the player there is an issue with New Mauville, and requests that the player visit him in his Mauville Hills apartment (granting the player access to the Mauville Hills elevator at the same time). In his apartment, he requests that the player press the button on the computer at the back of the facility; he then takes a photo of the player character's eyes and submits the picture to the New Mauville's gate's eye recognition software as authorized personnel, allowing the player to open the gate anytime. If the player visits Wattson in his Mauville Hills apartment after pressing the button, he rewards the player with TM24 (Thunderbolt).
In Ruby, Sapphire, and Emerald, the facility is a labyrinth of doors. There are green and blue doors, which only open when the corresponding button color is pressed; these buttons are found on the ground throughout the facility. However, the two types of doors cannot be open simultaneously.
In Omega Ruby and Alpha Sapphire, New Mauville instead extends 69 floors underground, but the player can only access the first floor, and only two rooms of that floor. There is a front room, which is located at the facility's entrance, and the generator room, which is accessed through the open door in the northwest of the first room.
Throughout the facility, there are some Voltorb that look like item balls.
New Mauville was designed by an ancestor of the Trick Master to deal with the foreseen overpopulation of children in Mauville City, which was already starting to happen by the events of the Ruby & Sapphire chapter.
In I'm Your Biggest Fan, Donphan, Sapphire accidentally came across the entrance to New Mauville and entered it along with Wattson and the Trick Master. After Sapphire had saved Wattson from New Mauville's robotic power generator, the power was turned on to reveal an enormous playground designed for children, which was put into use soon after. During these events, Sapphire also caught a Donphan and received a Dynamo Badge from Wattson.
Later, during the Ruby & Sapphire chapter, New Mauville was used a shelter for people when the Hoenn region was devastated by Groudon and Kyogre.