To walk through an ancient city is to listen to the whispers of monuments that have outlived their makers by millennia. There is a deep, evocative nostalgia in the sight of Roman harbours still braving the rhythmic lash of Mediterranean waves, or Mughal stepwells holding pristine waters deep within the sun-scorched earth of Rajasthan. Long before the advent of synthetic polymers, petroleum-based membranes, or computerised material science, master builders entered into an intimate dialogue with nature. They possessed a profound, intuitive chemistry-one written in volcanic ash, slaked lime, unrefined sugar, and sunken forests.