Which ancient city-state in southern Mexico flourished from 226 BC to AD 799?

The ancient city-state that flourished from 226 BC to AD 799 in southern Mexico is Palenque. This site is renowned for its impressive architecture, intricate carvings, and significant contributions to Maya culture during the Classic period. Palenque was a major power in the region and is known for its royal dynasties, including notable rulers like Pakal the Great. The city’s decline began in the late 8th century, but its historical importance endures through its well-preserved ruins and its role in Mayan civilization.

While Tikal is also a significant Maya center, it experienced its peak a bit earlier and later than the specified dates, and Cancuen, though important, did not have the same level of prominence during the given timeframe. The Popol Vuh, meanwhile, is not a city-state but rather a sacred text of the Maya that narrates their mythology and history. Thus, among the options given, Palenque stands out due to its defined historical timeline matching the question's criteria.