These give lots of XP and always contain rare or legendary gear. As you approach you will see that it has two stone statues of lionesses at the entrance, so you know you’re in the right place. You must loot the hidden treasure box in that location to solve the papyrus puzzle. Then look for a temple or any structure and mark the rough location on the map. For this you would have to climb up somewhere high and look for the pyramids to the west of where you found the papyrus.
Here’s an example: Usually they are things like “look west to the pyramids, between the dunes lies a temple guarded by stone lionesses”.