The Ultimablox Spire is a building located in the oceanic regions of Kaijuville on its own isolated island.
It is a spire-like building at 23,612 studs tall (or 6,727 meters approximately). It is so tall that sensitive Robloxians could experience shaking on their bodies on its higher floors, though altitude acclimatization would render their bodies adjusting back to normal if they stay on the upper floors for long enough.
It is over three times taller than the AirGojira Spire, making it the tallest building in Roblox, and taller than AirGojira Spire by a significant margin. The AirGojira Spire was planned to expand into space and set a new height restriction for Robloxia and would have dwarfed the building, but plans for the AirGojira Spire were scrapped on September 2025, meaning this building still remains the tallest building in Roblox.
It attracts 90 million tourists each year.
It is commonly (and jokingly) abbreviated as Kaijuville's Citadel (a reference to a video game) due to its immense height.