From Bulbapedia, the community-driven Pokémon encyclopedia.
The Hoenn region's Battle Tower (Japanese: バトルタワー Battle Tower) is a post-Pokémon League battle arena located in Hoenn's southeastern sea, inaccessible except by boat, as it connects to no routes. Its purpose is to challenge those who come to it, as the best and brightest Trainers from all over flock to it to see who is the strongest.
Carrying over its functions from the Johto region's Battle Tower in Pokémon Crystal, the Battle Tower expands further in Pokémon Emerald when it becomes one of the seven facilities of the Hoenn Battle Frontier, allowing for Double Battles, as well as Multi Battles (with the player being able to partner up with a computer-controlled Trainer or a linked human-controlled one).
This battle mode carries over the same rules and regulations as the Battle Tower that appears in Pokémon Crystal, expanded to include Generation III Pokémon. Players go through a series of seven battles in a row, with three Pokémon per side, with the levels varying depending on which mode is chosen. In level 50 and level 100 modes, all opponent Pokémon will be of the specified level, however, in "open level" mode, which replaces level 100 mode in Emerald, all will be the level of the player's highest-level Pokémon (with a minimum of level 60). No two Pokémon used by the same Trainer can be holding the same item.
In Emerald, Salon Maiden Anabel appears as the 35th and 70th opponent, the last battles in the fifth and tenth passes through the tower, respectively.
The rules of Single Battle mode apply to Double Battles as well, however, each Trainer uses a party of four, rather than three, and battles with two Pokémon at once. This mode appears only in Pokémon Emerald, however, Anabel does not appear, as she only challenges the player during Single Battle mode.
In multi battles, rather than having two Trainers using two Pokémon at a time, four Trainers use one Pokémon apiece in a Double Battle. Only two of the player's Pokémon are allowed to compete at once (with the same rules followed as before). This mode can either be used alone (where the player is accompanied by an apprentice or another computer-controlled Trainer) or when linked to another copy of Pokémon Emerald (via the Link Cable or Wireless Adapter accessories for Game Boy Advance), where another player contributes his or her Pokémon.
Any Pokémon can be entered for battle, except for the following Pokémon:
In the Battle Tower, a prize will be given away after each set of seven matches. A single, random prize will be given away, depending on the length of the player's winning streak.
Streak of 7-35
Streak of 35 or more
After reaching streaks of certain lengths, special prizes will be given out.
In the anime
The Battle Tower in the anime
A Battle Tower appeared in Destiny Deoxys, in LaRousse City, where Ash and Tory Lund battled Rafe and Sid. Like most things in the city, this Battle Tower was almost completely high-tech.