This page of the Far Cry 6 game guide contains a walkthrough of the Treasure Hunt for Ida's Triada Relic available in Madrugada.
District: Monjas Valley.
You will start this mission by reading the note on the wooden beam just before the cave entrance.
Start by climbing the rope. There are white arrows on the rocks that will lead you all the way to the end of the cave. This task is rather simple and forgiving, although it requires a bit of dexterity.
You will need to use rocks and ropes the whole way. Keep an eye out for arrows and light signals that appear in the area. They will lead you to your destination.
Eventually, you will see pink and purple smoke. These indicate the end of the cave, where you will discover the relic. Once you collect the relic surrounded by purple smoke, this location will end.