Known. Mounds and a stone channel for water were found under the forest.
The place is San Francisco de Pachijal, in Ecuador. Laser scans found more than 200 mounds and 100 terraces. Near the San Francisco River, researchers opened a sunken building with stone walls, an entrance, and a water channel. The style matches the Yumbo people, who lived in this north-western Andean region from about 800 BC to AD 1660.
The page does not say what is still argued.
https://www.ancient-origins.net/news-history-archaeology/lost-culture-ecuador-00102426