Tower of Obelisk, a place where many treasures and dangers are hidden.
For as long as the dungeon existed, the Tower of Obelisk has also been there. That means that in this world, for as long as mankind has existed, the Tower of Obelisk has always been there.
However, no matter how long this thing existed, no one knows the actual depth of the tower. The highest floor that anyone had explored was 54 by a group of Rank-SS led by a Rank-SSS hundred of years ago.
Similar to the Dungeons, the Tower Of Obelisk has lots of monsters and a boss on each floor. One might even call each floor an independent dungeon.
To proceed to the next floor, the Explorers could either kill the boss monster or search for the teleportation circle which is randomly scattered across each floor.
However, unlike the dungeon, monsters do not come out of the tower no matter what. Even if the Tower is left untouched for years, nothing will change.