The Louvre Abu Dhabi will open its doors to visitors in 2015, but one of the most crucial phases of construction is well under way. James Langton visits the site to see the foundations laid for a building that will stand poised between sea and sky. Driving along a barren sandy track that runs across the western tip of Saadiyat Island, the eye is pulled back and forth by the promise of two competing but compelling visions of the future. Farthest away on the right, a hoarding announces the site of the Zayed National Museum. But looming much larger through the left windows of our small convoy of SUVs, is a fence hung with a series of images of light-speckled spaces shimmering with the dual reflections of sun and water. Suddenly the lead vehicle stops at a break in the fence, where a small viewing platform for visitors has been erected, shaded against the fast-climbing heat of the midmorning May sun. Here, to a backdrop of the city\'s haze-shrouded skyline, we can at last see how the vision of the Louvre Abu Dhabi is giving way to reality. Below us is a vast depression framed by man-made sand dunes and filled with such activity that it takes more than a moment for the mind to focus. In the centre are five canary-yellow tower cranes. A sixth is in the process of being assembled, its bright steel bones laid across the ground. To the right, a dark monolith rises, shrouded in scaffolding. In the distance, another identical tower reaches skyward. Moving among them, in a pattern that clearly has meaning but cannot easily be unravelled by the untutored, is a small army of blue-suited workers. They are matched by dozens - no hundreds, actually thousands - of much smaller pillars emerging from a concrete platform that in places has turned a vivid green. Many of the pillars are now buried to their necks, topped with a circular spray of metal bars like fantastic surrealist house plants. Watching from a distance, there is a sense of order and surprising quiet. But to properly make sense of this, you need a man like Peter Armstrong. A laconic Canadian who has spent a decade and a half on UAE construction sites, Armstrong is the project manager for Turner Construction, whose curriculum vitae includes the Burj Khalifa and the Emirates Palace. Here, Armstrong explains, are the deepest foundations of the Louvre Abu Dhabi, seven metres below sea level, the Arabian Gulf held at bay by walls of concrete while powerful pumps that ensure the groundwater table is always below the site. In the end they can be removed, but turn off the pumps right now and eventually the museum could risk becoming a lake. Keeping the site watertight both now and in the future is one of the great challenges of building the Louvre Abu Dhabi. Yet it is one that few visitors will observe or appreciate. When Jean Nouvel\'s stunning design is made real, the sea will be allowed back to lap around the museum\'s walls. Anything more and it will be a very unwelcome guest in the galleries. When it is completed, two years from now, from afar the museum will resemble a vast floating disk pierced with light. It is a design that will balance two colossal forces - the weight of gravity bearing down from the 180-metre-wide dome against the pressure of the water as it pushes against the building\'s foundations. Armstrong describes this process as similar to \"taking an empty bottle and pulling it under the water\". To keep everything in place, the Louvre Abu Dhabi must sit solidly on its foundations, while retaining the illusion of weightlessness. Otherwise, says Armstrong only half-joking, \"it would float out to sea\".