Dark Souls 3: Drive secret areas to Forgotten Tombs and Archdragon Peak
Let's see how to find two important secret areas of the game.
You must know that in Dark Souls III there are two secret areas which is quite difficult to access if you do not know the entrance. These areas are the Forgotten Tombs and the Archdragon's Peak.
Forgotten Tombs
To get access to this secret area you need to beat the "Oceiros" boss (if you have difficulty follow the guide to beat all the Bosses of Dark Souls 3). After doing this, open the door in the area where the fight with the boss Oceiros took place and follow the path into the next room. There is a "fake" wall behind a chest, hit it to make it disappear and then have access to the secret area. Here is a video showing it all:
Archdrago Peak
To get access to this secret area you need to beat the "Oceiros" boss (if you have difficulty follow the guide to beat all the Bosses of Dark Souls 3). After doing this, open the door in the area where the fight with the Oceiros boss took place and take the "Old dragon" gesture that you will need later on.
Now travel to the Irithyll Dungeon, go through the area until you come to a lookout point with a dragon statue (there is also an elevator nearby). Use the gesture of the old dragon near the statue to start a cutscene, soon after you will arrive at the secret area of Archdragon Peak. Here is a video showing it all: