In order to find this location, you will have to travel to the point that is halfway between the Dune of Elusion and the Dahri Valley. Here you can find a pyramid-shaped building inside the mountain wall that you can easily identify.
Then you will have to go to where the main door is, in it, you will find a cube-shaped structure with which you can interact to obtain a scene. Go to the Eremite character in the game to get the password, which you can hear when you are in the base. The password is Marg bar parvezravan.
Now that we have reached the end of this guide on how to enter Thutmose's secret base in Genshin Impact we hope we have been as helpful as possible to quickly find this location.