Saudi Arabia’s latest megaproject is a mammoth 400 metre cube. The Mukaab will house a central spiral tower and boast two million square metres of floor space for retail, office and cultural uses. Cubic buildings are rare, mainly due to their inefficient land use. But in the Riyadh desert, anything seems possible, and work on the Mukaab has now begun. If completed, it will be the largest building in the world by volume. If being the key word. Saudi Arabia has boldly supported record-breaking engineering projects before. Examples include Jeddah Tower – designed to be the world’s tallest skyscraper – and The Line, conceived as a mirrored city in the desert 170 kilometres long. But follow-through is foggier. Jeddah Tower remains half-built after construction halted for five years in 2018, and The Line has been slashed to a mere 2.4 kilometres long for now (the Saudis deny this). Are the Saudis just too ambitious? Maybe, but the US can’t say a word. They built The Pentagon.