A team of experts headed by Slovenian archaeologist Ivan Sprajc has christened the site Chactun, Mexico's National Institute of Anthropology and History, said.
"It is one of the largest sites in the Central Lowlands, comparable in its extent and the magnitude of its buildings with Becan, Nadzcaan and El Palmar in Campeche", Sprajc said in a statement.
The complex covers more than 22 hectares.
Based on the number of monuments, at least 10 of them with inscriptions, the city is believed to have been the seat of government for a extensive area during the period of 600-900 A.D., the researcher said.
The INAH-backed exploration is financed by the National Geographic Society and two private companies, Austria's Villas and Slovenia's Ars Longa.
Down through the centuries, Chactun remained hidden in the jungle on the north of the Calakmul Biosphere Reserve.
The millennial metropolis is one of the nearly 80 sites detected by the Southeast Campeche Archaeological Recognition Project, launched in 1996.