The Fields of Air were located on the outskirts of Mahri Nui, on the same landmass as the village. This area teemed with plants called "airweed" by the Matoran. The Matoran used hyrduka to harvest air from here.1
Notes
Airweed grew in the undersea Fields of Air near Mahri Nui.2
The Fields of Air were an area adjacent to Mahri Nui where airweed grew.3
The Fields of Air were located outside of the Mahri Nui bubbles.4