Air temple sanctuaries

The air temple sanctuaries are large, ancient chambers located in the Southern and Northern Air Temples that can only be opened with airbending. They were considered important to the Air Nomads as a place where knowledge of the Avatar and the Avatar's previous incarnations were kept. Only the Avatar and the members of the Council of Elders were allowed inside.

History
Monk Gyatso, Aang's mentor, confided in Aang that when he was ready, he would meet someone very special inside the air temple sanctuary who would guide him on his Avatar journey. However, Aang fled the Southern Air Temple before this could occur.



A century later, Aang visited the Southern Air Temple with Katara and Sokka, and, remembering what Gyatso had told him, Aang opened the sanctuary doors with airbending. Instead of finding a master to teach him, he came across a long line with statues of previous Avatars. He then saw his future pet lemur, Momo, in the doorway behind them. Aang and Sokka raced to catch Momo, with Aang wanting to befriend him and Sokka wanting to eat him. Aang then accidentally stumbled upon Gyatso's corpse, and his rage and grief caused him to enter the Avatar State. While in the Avatar State, the eyes of the statues in the sanctuary began to glow. When Aang calmed down, he and his friends returned to the sanctuary. Momo brought Sokka food as a gesture of friendship, and officially joined Team Avatar later.

Aang and his friends came across another one of these sanctuaries when they traveled to the Northern Air Temple. At first, Aang was unhappy with the changes the mechanist made to the temple, but after he saw how spirited the people who lived there were, he decided to open the sanctuary doors for Teo. When he opened them, however, he found nothing but Fire Nation weaponry.

After Team Avatar and their allies had launched an unsuccessful attack on the Fire Nation, the youngsters of the group were forced to flee, and took refuge in the Western Air Temple. While there, The Duke, Haru, and Teo set out exploring, the latter remarking that he wondered if the temple had a sanctuary as well.

Tenzin's family visited the Southern Air Temple's sanctuary to start their vacation. Once there, Tenzin brought his children to its sanctuary. Jinora was in awe upon seeing the statues of the past Avatars, and more so upon seeing her grandfather's. Ikki and Meelo raced inside the room by air scooter, until Meelo crashes to an Avatar statue, obliterating it.

Southern Sanctuary


The sanctuary in the Southern Air Temple consists of a very tall, circular room. A statue of every single Avatar that came before Aang circles the room in a large swirl, in the fashion of the Air Nomad insignia. The sanctuary door is large and made of thick wood, and can only be opened with airbending. The statues of all the Avatars are lined up according to the Avatar Cycle.

Northern Sanctuary


Located inside the air temple, this great hall was originally built as a spiritual place, and only a master airbender could open the door to the sanctum. Because of this, Aang thought it was the only part of the temple that was untouched. However, as it turns out, the mechanist ingeniously used physics and clever mechanics to open it. Until he was caught by Team Avatar, the mechanist used the sanctuary as his secret weapons laboratory.

Trivia

 * The Fire Temple on Crescent Island also had a sanctuary door, and similar to how the air sanctuary door could only be opened with airbending, it could only be opened with firebending.
 * Of the named Avatars preceding Aang, Avatar Roku's statue is the only one shown to be in its proper place in the Avatar Circle depicted within the Southern Air Temple's, as Kyoshi's statue was not next to his, and the other confirmed Avatars were not shown at all. In The Legend of Korra's second season this seems to have been corrected.