While a Monument existed in Avant Gardens' predecessor, Nimbus Park, it bore no resemblance to the Monument in Avant Gardens, as it was simply a small scenery object, depicting several LEGO bricks. A contest on the LEGO Universe website was held to gather ideas for the Nimbus Park monument, with the winning entry becoming the Monument used in the released game. However, when Nimbus Park was redesigned into Avant Gardens, the Monument was replaced entirely and the contest winner's design, "Boundless Possibilities" by turtlefan014, was simply included as a model sold by Brutus Speck.
In the initial redesign of Avant Gardens, the Monument shared the same general design of that in the released world, but with slight differences such as the addition of spike pistons for obstacles. The area around the Monument was also different in design, with tower cranes working on constructing the elevated highway around it.
In an early version of the Avant Gardens story, it was said that the Monument was a clue to discovering who the Minifigure's ancestors were and what enemies they faced, as the Monument was an ancient relic being excavated, not a modern project.
It is possible to get to the top of the Monument without using any Imagination, and hence without using any Quick Builds.
The Maelstrom monster carved into the Monument can also be seen in the background art at Red Blocks in Nimbus Station. This is likely due to the fact that at one point Red Blocks was also located in Avant Gardens.
The Monument in Nimbus Park
UltraHypnoToad - LEGO Universe Monument
The Monument in a prototype of Avant Gardens
The first publicly released image of the Avant Gardens Monument