The Oasis is the unique faction structure for the Gerudo. It rapidly increases population growth for its host settlement. An Oasis cost 5000 rupees and requires and least a City-level settlement to construct.
In a land of death and famine such as the Gerudo Desert, water is a most precious and rare resource. The Gerudo have adapted to surviving on as little water as possible, but when the time and resources are available the Gerudo can build an artifical oasis in their cities to provide for its people.