I never really understood what a Oasis was, I thought it was a bit of a cliche, something akin to a mirage, a convenient plot point in the script a way of saving our cast from a fate worse than death, or at least the fate of death.
Or maybe it was a sugary treat that got me through my university years, heavy glass bottles a lid which popped as you opened it. A ad campaign that gave us a repeatable line about Tea Cosies but looking back was a just a little bit racist.
But Oasis exist, they are simply planned or maybe nature irrigation in deserts that allow for plants to be grown. Like this one a man made pond at the bottom of the valley and the Date Palms all around it and of course with a farm comes a city.