The Ark in the cartoon continuity carried the Autobot and Decepticon armies to Earth. In the american G1 cartoon, the Ark was the Autobot's HQ.
Later it was revealed that the Ark was stranded in the Dead Universe.
In the near end of the second season through out third season of the Beast Wars, Megatron reveals a hidden message sent by the Original "G1" Megatron had left a message to any Decepticons who survived the Great War a.k.a. "Transformers G1" series, Ravage, a survivor and now a Tripredacus Agent sent to capture the rogue Predacon witness the message sent by his former leader and sided with Megatron to destroy the Maximals and carry whatever the plans Megatron planned to do on earth. After the demise of Ravage, Blackarachnia and Silverbolt discover the the Ark after digging near a mountain, which later reveals to be the volcano that will wake up their ancestors in 1984 and continue their battles. Megatron gets their before the other Maximals, he plans to destroy the great leader of the Autobots, Optimus Prime destroying the Maximals and Autobots, by erasing them from time itself once and for all. However, Megatron plans fail due to Optimus Primal fusing the spark of Optimus Prime with his own and resulting in an Optimal Optimus, Primal then restores the spark of Optimus Prime Back into the matrix within his body, later they began building a new base, due to Rampage pulling it into a waterfall, they hold their ground within the volcano to defend the Ark, against the Predacons in order to ensure a future for all Transformers.
The Ark is made up of 4 ships of Atlantis 1 for each of the 4 planets, Earth, Speed Planet (Velosotron), Jungle Planet and Gigantion.