It depends where you are after the 7th gym it is in a secret base that you stupid people should know how yo find it
You can't
Team Magma Hideout
you can find him at the top of the volcano a couple gyms after you fight the leader of team magma
On Mt Chimney to find it you need a magma emblem which you will get on Mt Pyre.
You will need to defeat the Team Aqua or Magma grunts in the Seafloor Cavern and make your way though their ranks to the leader of Team Aqua/Magma.
This is not the team magma cave that is team aqua cave. Team magma cave opens when you have the magma symbol.
he is at meteor falls with a few team magma members he gives the team magma members a meteorite the Archie and team aqua shows up team magma runs away then prof. Cozmo gives you something and then you have to go to mt. chimney and fight Maxie
You kick their asses and if I'm not wrong you find groudon
In the mountain after defeating the team magma leader.
run for your life you cant find it
Team Magma and Team Aqua aren't even featured in Pokemon Diamond and Pearl. If you are looking for Team Galactic bases, you will find those throughout the region in Cities such as Veilstone and others. If you want Team Magma's and Team Aqua's base in Ruby and Sapphire, it is just off the beachead in Lilycove city.
In Pokemon ruby, your rivals are team magma, not team aqua, so you cannot find Archie, only maxie.