Associated Press
Ancient builders across the world created structures that are still standing today, thousands of years later — from Roman engineers who poured thick concrete sea barriers, to Maya masons who crafted plaster sculptures to their gods, to Chinese builders who raised walls against invaders. A growing number of scientists have been studying materials from long-ago eras — chipping off chunks of buildings, poring over historical texts, mixing up copycat recipes — hoping to uncover how they’ve held up for millennia. This reverse engineering has turned up a surprising list of ingredients that were mixed into old buildings — materials such as tree bark, volcanic ash, rice, beer and even urine.