Known. Scans found a large building under the main plaza at Monte Albán.
Monte Albán is in Oaxaca, Mexico, about nine kilometres west of Oaxaca City. The city was founded in 500 BC and declined around AD 850. The main plaza was built and rebuilt for more than 1,000 years. Under it, ground scans mapped a buried building. It is like temples found at the site in the 1930s.
The page does not say what is still argued.
https://www.ancient-origins.net/news-history-archaeology/monte-alban-0014601