There are checkpoints scattered across Far Cry 6's map, most of which contain bad guys and some FND crates to crack open. One of those is in the Aguda Cliffs named location. If you're wanting to get the goodies inside, here's a guide on the Aguda Cliffs Checkpoint Key location in Far Cry 6.
Where to Find the Checkpoint
Aguda Cliffs is near the western coast in the north-west area of Far Cry 6's map.
The checkpoint is on the main road going towards the base right by the coast. It's pretty tough to miss.
Aguda Cliffs Checkpoint Key Location & Bug
You'll come across an issue when you get there, though. For at lot of players, it simply won't let you capture the base.
The key should be being held by one of the enemies there, so just killing them all should allow you to unlock the door.
However, players are taking out all of the bad guys, finding no key, and then being left without any option. What seems to be happening is the Aguda Cliffs Checkpoint isn't spawning as a proper checkpoint, so you're not able to capture it. Hopefully Ubisoft fix this issue sometime in the near future.
How to Get the FND Crate
However, that does not mean you cannot get to the FND Crate and the loot inside. The door may ask for a key to open it, but some explosives and the door will come right off its hinges.
Find yourself an RPG, a tank, or even an explosive Supremo ability, and aim them at the door. Rain down fire and the door should simply be open once the smoke clears.
You'll then be able to head inside, grab the loot and head on your merry way. It won't have registered that you've caught the checkpoint, but you'll at least have the loot you were after.