Buenos Aires is the capital of Argentina.
The tech conglomerate Onyx had a tower in Buenos Aires.
After the people of Verenya had been mutated into partial Dire Wraiths, Garrison Blackrock arranged for the Action Man Programme to take the citizens to the Onyx tower in Buenos Aires in the hopes a cure could be found. Once the Revolutionaries and the Micronauts took custody of the Talisman, Blackrock had Larissa take it to the tower as well for study. After meeting and befriending the lost Eukarian Centurion, Blackrock directed him to the Onyx tower to recover.
After the Revolutionaries captured Garrison Kreiger and reunited with the time lost Sgt. Savage, they retreated back to Onyx tower to await a G.I. Joe squad to take custody of the Talisman. Centurion, however, was still loyal to Kreiger and disabled the tower's defences, allowing Baron Ironblood's forces to teleport into the tower. Heroes and villains fought for the relic before Savage unmasked Ironblood as none other than Joe Colton himself.