As you traverse Fontaine, you'll undoubtedly come across numerous open chests, which will likely accumulate a substantial number of Hydro Sigils over time. In this guide, you'll learn where to exchange these Hydro Sigils.

Fontaine Luquin's Location: Where and How to Exchange Hydro Sigils

You've encountered similar places before, like the Frostbearing Tree in Dragonspine, the Sacred Sakura in Inazuma, the Araumi Whirlpool in Sumaru, and others. These locations allow you to exchange seals for numerous rewards, including Ascension Materials, weapon blueprints, Submerged Palace keys, mora, weapon enhancement materials, and more. In Fontaine, this role is fulfilled by a fountain, located at the address shown in the image below.

Screenshots taken from ZaFrostPet