A few months ago, I visited Angkor Wat, the majestic temple in present-day Cambodia that once stood at the centre of a vast empire. As the five towers of the palace came into view, I was, despite the intense heat, fully immersed in the beauty of the place. I imagined how excited a visitor from a faraway land in the 12th century, full of anticipation for a meeting at court, would have felt arriving at what was then the largest settlement on Earth.