The Taj Mahal was built in the 17th Century by the Mughal emperor Shah Jahan, in memory of his late wife. The extraordinary marble mausoleum was built in the city of Agra in northern India, and is considered one of the seven wonders of the modern world. And yet, there are so many things we still need to learn about the Taj Mahal and the surrounding architectural complex. How did the builders complete it in just 20 years – when the Notre Dame cathedral took more than a century? What gives it stability, built as it is on the unstable banks of the sacred river Yamuna? Using satellite images and microscopic investigations, historians, researchers, and engineers uncover the answer to these questions and more. The latest technology finds evidence of deep foundations, intricate gemstones, and innovative brick manufacture, and reveals the secrets at the heart of the colossal construction.