Ars Technica's Annalee Newitz visited the Cahokia Mounds archaeological dig site near St. Louis, Missouri and talked with archaeologists about unearthing the remains of a burned mat that was part of a larger burned offering to the gods. Read the article: http://arstechnica.com/features/2016/12/theres-a-1000-year-old-lost-city-beneath-the-st-louis-suburbs/