Jalendu Temple is a Kyrat temple from Far Cry 4 that returns in the Pagan: Control DLC for Far Cry 6. In the DLC, it is one of three places where Pagan must recover a piece of his mask.
The DLC takes place inside Pagan Min's mind. To escape, he has to collect three pieces of his mask, and Jalendu Temple holds one of them.
In Far Cry 4 the temple sits on an island in a lake in northern Kyrat. It is where the Tarun Matara ceremony was held, in which young girls were chosen as living goddesses.
Pagan remembers storming the temple with a rifle and stripping its gold. He hated a tradition that harmed young girls, as Ishwari had been harmed.
If you back Amita in Far Cry 4, the temple is destroyed. If you back Sabal, a secret scene shows him executing Amita's and Pagan's followers here.