Ancient Key is a Quest Item in Fontaine that can only be obtained during the Aqueous Tidemarks World Quest in Genshin Impact 4.0! Learn the location of the Fontaine Ancient Key and how to use it in this guide!

Fontaine Ancient Key Location

Institute of Natural Philosophy, Court of Fontaine

The Fontaine Ancient Key is found underwater in the Liliacruces Forum, before reaching the entrance to the Institute of Natural Philosophy, located south of the Court of Fontaine.

The Ancient Key can only be obtained during the Aqueous Tidemarks World Quest, which you can start by talking to Virgil near the court's Statue of the Seven.

How to Get Fontaine Ancient Key

Obtain During Aqueous Tidemarks

Aqueous Tidemarks Location

The Ancient Key Quest Item can only be obtained during the Aqueous Tidemarks World Quest, and thus the entrance to the Institue of Natural Philosophy can only be opened during the same quest.

Where to Find Virgil

Virgil is found near the Statue of the Seven in the Court of Fontaine. The World Quest is available as soon as you reach the statue in Palais Mermonia.

Aqueous Tidemarks Quest Guide

Defeat the Hunter's Ray Guarding the Chest

Three Hunter's Ray are guarding the chest in the middle of the room and you'll have to defeat them to get the Ancient Key.

Use your Transoceanic Sourcewater ability to obtain the water blades attack from the nearby Xenochromatic Hunter's Ray (the blue one with a mark) and defeat the three green Hunter's Ray.

Xenochromatic Creatures and Abilities Guide

How Do I Get the Ancient Key if I Already Opened the Chest?

If you have opened the chest prior to starting the quest, the Ancient Key will be in another part of the room during the quest. It can be inside a ball of Seaweed that you need to cut down.

You can still trigger Aqueous Tidemarks and follow the objectives until you reach the entrance to the institute, past the teleport waypoint.

How to Use the Fontaine Ancient Key

Open the Gate to the Deeper Section of the Ruins

You can use the Fontaine Ancient Key to unlock the door leading to the deeper sections of the Institute of Natural Philosophy. Again, this area, as well as the key itself, is only accessible during the Aqueous Tidemarks quest.

Bring the Ancient Key to the lock mechanism and unlock the gate to explore more of the underwater area where you can find a few of the Hydroculi!

Genshin Impact Related Guides

Items and Materials

Other Fontaine Quest Items

All Fontaine Quest Items
Tears Among the Stars	“Delightful Encounter”	Arkhium Lumenite
Arkhium Stock	Thelxie's Fantastic Adventures	Mysterious Ore
Credit Coupon	Drained Conch Cup	Energy Concentrating Component
Foggy Forest Branch	Fontaine Ancient Key	Handwheel
Mysterious Core	Mysterious Xenochromatic Crystal	Punched Tape
Rainbow Rose's Ideals	Rusty Iron Key	Simple Vault Key
Spur Gear	Strange Part	Teardrop Key

List of All Quest Items

List of Quest Items