A gold-crowned obelisk rises from Southbank like a measuring rod for the sky, its red stripe slicing across the façade as if marking a high-water line for the Yarra below. Once the tallest residential building in the world at completion in 2006, it stacks hundreds of apartments above the river in a sheer wall of reflective glass. At its summit, The Edge projects outward in a transparent cube, suspending visitors above Melbourne like a crystal balcony over the void.