Sky Pillar

The Sky Pillar is a huge tower located in Hoenn located at Route 131. Appearing in Pokémon Ruby, Sapphire, and Emerald, it is the only place in the game where the player can fight (and catch) Rayquaza. Many other species of high-level Pokémon also inhabit it, such as Dusclops and Altaria. The Mach Bike is needed to climb it, and is accessible in Ruby and Sapphire. In Emerald, it is accessible at the second time after you have woken the Rayquaza to confront the Groudon and Kyogre in Sootopolis City. You do not need to challenge the Elite Four to catch it.