Every 1,000,000+ Eastern Chinese City on a Map

"(Urban) agglomerations and metropolitan areas include a central city and neighbouring towns (suburbs) forming a connected region of dense, predominately urban population. Their population is economically and culturally linked to the central city (e.g., by commuters). Some agglomerations and metropolitan areas have more than one central city (e.g., the Northern Pearl River Delta or the Ruhr region). Mostly, the components of an agglomeration are small administrative divisions like communes; the gaps between built-up areas are small (e.g., less than 2km)."

I'd say that the Shanghai area applies to this definition, especially with the cities of Wuxi and Suzhou between it and Changzhou.