The Oasis is an area in the world Pride Lands. This is where Pumbaa and Timon spend most of their time.
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The Oasis.
This is also the place where Simba has been all these years, after his father died, believing that he killed his father.
When Sora escapes from Scar at Pride Rock, he meets Simba here. This is also the spot where Simba has two epiphanies. The first one is that Simba shouldn't run away from his past. The second is that he should not doubt his actions.