Avalon
Avalon is by far the world’s tallest building, standing 3.22 kilometers (10,560 feet) above sea level - nearly four times taller than the second tallest building in the world - with 400 floors of varying heights, including multiple single floors as high as several average floors, and extending a further 60 meters (197 feet) below sea level with another 12 floors, its hexagonal base occupying an area of 248 meters (813 feet) at its widest points, located in the center of Ilmaria. It serves as a critical supportive element and method of travel between levels of the country’s two-tiered structure, a workspace for approximately 40% of the country’s working population, the central provider of utilities for the entire country, a large commercial hub with many spaces and even entire floors available for lease, a provider of 1,524 residential apartments, the headquarters of 11K, the largest and most powerful data center in the world by an order of magnitude, and the national capital.
It is constructed, like the rest of Ilmaria, primarily out of composite materials, most of which are trade secrets held by 11K. The only composite material that is publicly known in full detail is the carbon fiber and titanium blend used for minor structural support. A structure like Avalon was thought to be completely impossible before 11K constructed it, and due to the sheer power of 11K allowing them to circumvent legal requirements for building code and the publication of construction methods, how they did it remains a mystery subject to feverish analysis and investigation.