Chicago-based firm Adrian Smith + Gordon Gill (AS+GG) has officially been announced as the design architects for the Kingdom Tower that is to be built in Jeddah, Saudi Arabia. Initially planned to stand one mile (1.6 km) high and be called the Mile-High Tower, the building was scaled down after soil testing in the area in 2008 cast doubt over whether the location could support a building of that height. Now the building will stand over 0.62 miles (one kilometer) tall, which will still allow it to overshadow the 2,717 ft. (828 m) Burj Khalifa to claim the title of the world's tallest building.

The Kingdom Tower will be the centerpiece and first construction phase of Kingdom City, a 57 million square foot (5.3 million m2) development located along the Red Sea north of Jeddah, which is known as the traditional gateway to the holy city of Mecca. The entire development has been budgeted at US$20 billion, with the Kingdom Tower alone costing approximately $1.2 billion to construct and covering an area of 5.7 million square feet (530,000 m2).

The building will contain 59 elevators, including 54 single-deck and five double-deck elevators, as well as 12 escalators. The elevators serving the observatory will travel at 22 mph (36 km/h) in both directions. At level 157, a sky terrace roughly 98 feet (30 m) in diameter intended as an outdoor amenity for use by the penthouse floor extends from the side of the building.

The exterior wall system is designed to minimize energy consumption by reducing thermal loads, while a series of notches on the building's three sides create pockets of shadow that shield areas of the building from direct sunlight and provide outdoor terraces.

The three-sided tower rises from a three-petal footprint design with aerodynamic tapering wings that help reduce structural loading due to wind vortex shedding. Gill says the tower's sleek, streamlined form was inspired by the folded fronds of young desert plant growth.

"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," added Smith.

While the building's exact height isn't yet known, when completed AS+GG claim it will be at least 568 feet (173 m) taller than the Burj Khalifa, which was also designed by Adrian Smith when he was at architectural firm Skidmore, Owings & Merrill (SOM). At SOM, Smith also worked on the design for the Pearl River Tower, while AS+GG also recently won an international competition to design China's Wuhan Greenland Center.

AS+GG says design development of the Kingdom Tower is underway, the foundation drawings are already complete and construction is set to begin 'imminently."