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Btvs.png Although this article is based on canonical information, the actual name of this subject is conjectural.
The tower was built by crazy people and I don't think it's holding up very well
Dawn Summers[src]

This tower was a crude structure built by Sunnydale's mentally-ill population, including the victims of Glorificus, mystically attracted by the coming of the "Big Day". Despite being completed in less than one day, the structure was several stories tall.

The purpose of the tower was to serve as a sacrifical place for Dawn Summers, who was supposed to be bled by The Abomination in order to spill her blood into a specific location at an specific time. As Dawn's blood contained the energy of The Key, it would shatter the walls between realities, allowing the hellish goddess to return to her home dimension.

View of the Tower

When the Scooby Gang stormed the tower with the goal of saving Dawn and preventing Glory from performing the ritual, the Tower was heavily guarded both by Glory's Minions and the "crazies". As the Scoobies and Glory's followers fought, the demon Doc, also a worshipper of "The Beast", made his way up the tower with the intent of completing the ritual since Glory had been stalled by the Slayer. Spike attempted to stop the demon, but was defeated and thrown from the tower. Doc was also thrown off the tower by Buffy, but he had already managed to make shallow cuts across Dawn's stomach. The blood reached its intended destination and the walls separating dimensions shattered for several minutes, until Buffy sacrificed herself to close the tearing in reality's fabric.

Months later, the newly resurrected Buffy Summers walked all the way to the tower, as it was the last place she remembered. By this time the tower had become unstable since it had been built hastily by the "groupies". The tower ended up collapsing, but having to save Dawn from the collapse restored Buffy's memory.