Nearly a hundred and fifty years ago, when railway lines were being laid down for the first time in the Punjab, engineers stumbled upon the site of Harappa in present-day Pakistan. To them, it seemed like a mound that was a rich source of ready made, high quality bricks. So they carried off thousands of bricks from the walls of the old buildings of the city to build railway lines. Many buildings were completely destroyed. Then, about eighty years ago, archaeologists found the site, and realised that this was one of the oldest cities in the subcontinent.