Diodurum Ruins Roman Excavation is one of the Assassin’s Creed Valhalla Melunois Mysteries you’ll need to complete in the first Siege of Paris DLC area.
The AC Valhalla Diodurum Ruins Roman Excavation activity we’ll cover in the guide below allows you to collect the Diodurum Key, which you’ll use to open the door to the Hidden Ones’ Bureau in Paris.
The Roman Excavation Mystery in Diodurum Ruins is in the same place as the Diodurum Ruins Fast Travel point; you’ll need to synchronize. As you can see on my map, you can find it in the northern section of Melunois, just north of Chartres Church.
How To Complete the Diodurum Ruins Excavation Mystery
As said, to finish this Mystery, your goal is to find and collect the Diodurum Key, which happens to be in the same room where you can find the Golden Flame Ability or the Book of Knowledge. So basically, if you reach the location of the Ability, you’ll also find the Key.
This means you’ll use the same method to get inside and start by performing a Leap of Faith in the pond under the High Point after you synchronize it. Next, you’ll need to dive and follow the underwater tunnel, which leads to a dead-end.
From there, you’ll swim up and enter a new tunnel where you’ll see the Hidden Ones’ logo on a stone door. Interact with it, and in the next room, you’ll see a gap filled with water. Jump, then swim right, following a new underwater tunnel.
You’ll need to take two left turns to reach a new dead-end and swim into a room with a breakable wall like the one in my screenshot. Here, turn around to spot a red jar you can throw to destroy the wall.
Behind the wall above, you’ll find the room where the Wealth awaits you. Once inside, turn right, and you’ll spot the table below and the Diodurum Key on it.
After getting the Key, the Melunois Roman Excavation Mystery ends; however, you’ll notice that you’ll start a new quest.
How To Use AC Valhalla Diodurum Key
If this is your first Key, you should know you won’t be able to use it immediately because you’ll need the other two. Basically, the Diodurum Key, the one from Amienois and the one from Evresin, allows you to enter the Assassin Bureau in Paris, which is your objective for the Hidden main quest.
Until then, your next goal is to exit the ruins, which is extremely easy through the door on the left. If you encounter difficulties, simply follow the same path as the one outlined at the end of my guide on how to get the Diodurum Ruins Ability.