From Bulbapedia, the community-driven Pokémon encyclopedia.
Mt Pyre is a location in Hoenn. It has an interior and exterior section and is located on Route 122.
Mt Pyre can be considered a counterpart to Kanto's Pokemon Tower. It houses the many graves of Pokemon. Many grieving trainers also visit the Tower to pay their respect. Also present within the mountain are thrill seeking trainers who will battle the player when they come across him/her.
On the summit of the mountain, there live an old couple who are well versed with the legends of Hoenn. They also guard the Red Orb/Blue Orb which Team Aqua and Team Magma seek.
In Pokemon Ruby, Sapphire and Emerald, Team Aqua or Team Magma(depending on which game version the player is playing) will attempt and succeed to steal the Red/Blue Orb from the summit of Mt Pyre to awaken Kyogre or Groudon. After the player has subdued the legendary pokemon[s], the player can return to the summit to watch Maxie and Archie return the Blue and Red Orb to it's proper place.