On this page of the Far Cry 6 guide you'll find a detailed description of a treasure hunt And the Beat Goes On... available in the Valle De Oro region.
Subregion: Cruz Del Salvador.
District: Senal Ridge.
The quest begins once you enter the nightclub. The entrance is boarded up, but the planks can be easily destroyed with a machete.
At the very bottom, look up to throw the rope and reach a small ledge.
On the ledge you'll find a switch which opens the way forward.
It's time for a long climb to the treasure chest. Look around carefully and watch out for the current, carried by plentiful amounts of water.
Eventually you'll reach the top. It stands out thanks to the pink light, which is sure to catch your attention. Open the chest to complete the mission.