By the end of this decade the Kingdom tower will replace Burj Khalifa as the world's tallest building. The structure will extend to a mind boggling height of 1 kilometer(3280 feet) and will be constructed in Jeddah, Saudi Arabia. Designed by Adrian Smith + Gordon Gill Architecture, the building will house a Four Seasons hotel & apartment area, office space, luxury condos and the world's highest observatory. The building's spire shape was not a random choice. The architect explains:

With its slender, subtly asymmetrical massing, the tower evokes a bundle of leaves shooting up from the ground-a burst of new life that heralds more growth all around it. This symbolizes the tower as a catalyst for increased development around it. The sleek, streamlined form of the tower was inspired by the folded fronds of young desert plant growth. The way the fronds sprout upward from the ground as a single form, then start separating from each other at the top, is an analogy of new growth fused with technology. While the design is contextual to Saudi Arabia, it also represents an evolution and a refinement of an architectural continuum of skyscraper design. The three-petal footprint is ideal for residential units, and the tapering wings produce an aerodynamic shape that helps reduce structural loading due to wind vortex shedding. The Kingdom Tower design embraces its architectural pedigree, taking full advantage of the proven design strategies and technological strategies of its lineage, refining and advancing them to achieve new heights.

This is actually a sky terrace meant to be used as an outdoor amenity space for the penthouse floor on level 157.