This location is in The Scorched Lands. This is one of the most important locations in Assassin's Creed: Odyssey Fate of Atlantis - you reach it during the main storyline.
The entrance to this location is in the Kronos's Treasury. Jump into the big hole in the floor.
Immediately resurface and move along the way. There are no branching paths in this cave - you won't get lost.
Once you see the stairs, go up - they are presented in the screenshot above.
Hades' dogs are in the cave. Kill them. Otherwise, they can attack you by surprise.
Reach the end of the location to get the tablet. When you interact with it, you will end this location and one out of the three parts of the quest.