What is the Battle Frontier in Generation IV?

Diamond and Pearl ended their post-game at a single Battle Tower standing in the Battle Park. Platinum replaced that park, on the same ground north of the Fight Area, with a full Battle Frontier of five facilities, and HeartGold and SoulSilver then built the identical Frontier west of Olivine City, on the very spot where Crystal's Battle Tower had stood. No other Frontier in the series exists twice like this; a streak earned in Sinnoh follows exactly the rules of the same facility in Johto.

Each facility bends the battle rules one way. The Tower is the plain streak, three against three, climbing toward Tower Tycoon Palmer. The Factory hands you rental Pokémon and lets you swap one after each round. The Castle turns healing and items into a currency you spend between fights under Castle Valet Darach, who battles on behalf of Lady Caitlin. The Arcade spins a roulette board that can poison, paralyse or weather the field before a punch is thrown. The Hall asks for one Pokémon and lets you choose which type to face, streak after streak, under Hall Matron Argenta.

Victories pay Battle Points, and the Frontier Brains wait at fixed depths: beat one after 21 straight wins for the Silver Print, and again after 49 for the Gold Print, the framed certificates that replaced Emerald's Symbols. The Factory's Thorton and the Arcade's Dahlia complete the five bosses.

The Frontier is also a snapshot of the era's ambitions: a shared endgame across two regions, built for players who had finished everything else. When Generation V replaced it with a single subway, the five-part Frontier became the DS era's high-water mark for post-game design.