The Aerie is a small town in NieR RepliCant and NieR Gestalt (NIER) that overlooks a wide canyon, near the Northern Plains. The houses are connected by a series of large platforms, bridges and ladders. It is frequently shown to be barren, lacking any sight of its citizens, mainly due to their chosen isolation and fear of Shades, outsiders, and generally the unknown as a whole. However according to Kainé's backstory, it can be assumed that at a time, the village was active to an extent and isolation was moderate considering that some of its inhabitants were outside of their homes.
Interestingly, the houses are re-purposed shipping containers, with visible warning labels on their sides.
The Aerie was Kainé's hometown. Because she was intersex, she was ostracized by the superstitious townspeople and their children, who saw her very existence as a bad omen. After her parents passed away, her grandmother took her in and they moved to an area just outside of The Aerie. During the events of the game (particularly during the first half), the highly-strung townspeople are shown to blame Kainé for almost every misfortune that befalls them, such as when the Shade Hook was fought within the village itself, as they claimed she led it there on purpose.
Nier is instructed by Popola to travel to the Aerie to speak with the village chief. However, upon arriving at the chief's house, he would hear none of what Nier had to say. As he was departing from the village, he and Kainé were attacked by the shade Hook. 5 years later, Nier is told that the village has suddenly opened a large shopping center, much to everyone's surprise. When Nier speaks to a citizen and expresses his desire to destroy all shades, nearly all of the citizens were turned into shades and a giant one emerged from their defeated remains. After a fierce battle, the entire Aerie was accidentally destroyed by a berserk Emil.