Decarabian's Tower is located in the middle of the city of Old Mondstadt and is first scaled as part of the Archon Quest Empty Abode. As its name implies, it was where Decarabian, the God of Storms, once resided and overlooked his people.
The very bottom of the tower is treated as an Out of Bounds area; upon reaching a certain altitude on the lowest floor of the tower, the screen cuts to black. Players will then find themselves at the nearby wind current, and Paimon remarks "Watch out! Don't go near there!"
The top floor contains a Light Actuator and the domain entrance for Confront Stormterror, unlocked after completing the Archon Quest A Long Shot; the description for the domain implies that the domain area was where Decarabian personally resided.
To obtain the achievement "The Remains of the Gale" for reaching the very top of the tower, ride the wind current used to reach the top floor all the way to the roof of the tower. Then, climb the broken but intact pillar. (The other intact pillars will block you from reaching the top.)