People have devoted their entire lives to studying this, but I can give a very short overview: First, there's early colonial maps, such as the Mapa de Uppsala,

People have devoted their entire lives to studying this, but I can give a very short overview: First, there's early colonial maps, such as the Mapa de Uppsala, which give us a decent understanding of the city. Then there are the accounts of the arriving Spanish. There's also archaeological evidence all throughout Mexico City, though much has been actively destroyed.