Anthropology

Their ancient civilization declined politically, but the descendants of the old empire and their culture are still there - millions of them, speaking different dialects of the Mayan language and many of them still following some of the Mayan religious beliefs (except human sacrifice, of course), sometimes intermixed with Christian influences.

For comparison, the Roman Empire no longer exists, but Roman descendants still exist in Italy, speaking a language derived from Latin and following some cultural traditions in foods and family relationships.

The Spanish Empire no longer exists, but the Spanish people did not disappear.

Same for the British Empire.