The outpost_rio_classic.zip file you have requested: Maps Levels Missions / Halo Outpost Rio - 8.72mb is not available. Perhaps try browsing all files for the game Halo: Combat Evolved and upload any files you want to share or are missing. This is the only information we could locate:
Outpost Rio is on the side of a huge mountain. As such it is a very dangerous place to be fighting. Expect to fall to your death if you are not careful.