One of the most commonly known civilizations in ancient Mesoamerica are the Maya. They controlled a very large area of what is now called Mexico, Guatemala, El Salvador, and Honduras including the Yucatán Peninsula. It was the most successful civilization in that area before the Spanish conquistadors invaded and wiped out most of them. Although most people simply know them as singular ethnic and cultural group, the term Maya encompasses multiple ethnicities depending on where they came from.
Unlike the Olmec, the Maya did not vanish into history in some mysterious fashion. There is a very strong historical record of their cities being abandoned as the population dwindled. Historical researchers point to things like over farming, environmental collapse, and even volcanic activity as partial reasons for this decline. Eventually, the area was taken over by explorers from Europe and the Maya assimilated into the new culture. Descendants of these ancient folk still live today.