monolith
Definitions
A large single upright block of stone, especially one shaped into or serving as a pillar or monument.
A large, powerful, and intractably indivisible organization or system.
A single, massive, and uniform structure or entity.
Examples
The ancient monolith stood silently in the center of the desert, its origins a mystery to all who visited.
The company's outdated software system had become a massive, unmanageable monolith that hindered innovation.