Ancient History

I think there were just nomadic or semi-nomadic tribes 2000 years ago in Mesoamerica... No vast civilizations...

I don't think the Aztecs even existed back then... Tenochtitlan was founded in 1325...

Olmecs and I believe, Mayans but they may be about 1500 years ago

The Olmecs were actually advanced. http://en.wikipedia.org/wiki/Olmec
and well the Mayans, http://en.wikipedia.org/wiki/Maya_civilization

Ok. So when I looked at the claim that Tenochtitlan was the 'largest city in population' at its time, bells saying 'BS' went off in my head. Alors...
http://en.wikipedia.org/wiki/Nanjing

Yes, the dates end a little under a century before the arrival of the Spainish at Tenochtitlan, but the population only increased after the dates prescribed [it is still a massive city to this day and is the 'Beijing of the Southern Provinces'].

Thus Romulus dreams of Tenochtitlan being the most populated city at the time were dashed thanks to ever multiplying Chinese people.

Yep. In my experience [studying history] the Chinese ALWAYS out-number their aversaries. And the Chinese having some of the most populated cities has been a millenia-long trend. En fait, I don't think that anybody, except parhaps some Indian cites and some civilizations with little land room [i.e. Japan, England] have EVER had larger or even rivaling cities to the Chinese.

China has lost, but only briefly when there was a huge flood or great famine. For a couple years the Romans had the biggest. But when it comes to population China has always won in the ancient world.

Sorry to say this but Tenochitlan was the largest city LATER than Nanjing. The Aztecs were at their height around 1500's

The Aztecs got defeated in the early 1500s, 1519-1521 being there final years. Tough more of there deaths were caused by famine and disease brought to you by the spanish then by the spanish weapons (Which did some damage)

Reread my post. It depends on what you say Tenochitlan's 'height' was. Posts on this thread take its 'height' to be 200,000 people at approximately the arrival of the Spainish. That is lower than the population count for Nanjing prior to that time [1519] for which I said that it is a logical conclusion that Nanjing maintained a larger population up to that point in time from when the last census was taken placing Nanjing's population at approximately 487,000 people and they have grown to be a multi-million population at the current time.

The largest city at the year it was at its height and your site said until 1425.Viking: by the time Spain arrived it was 100 years ater Nanjing was at its height. Nanjing remained the capital of the Ming Empire until 1421, when the third emperor of the dynasty, Zhu Di (the Yongle Emperor), relocated the capital to Beijing. It is believed that Nanjing was the largest city in the world from 1358 to 1425 with a population of 487,000 in 1400 contradicted your entire arguement Imperial

You said 1500s in your post just saying.

No it doesn't.
If you actually read my post, you would be able to follow the logic.
Yes, the site that I cited only accounted up to a century prior to the height of the Aztec city of Tenochtitlan, but I was following the reasonable and logical process that leads to the conclusion that the city of Nanjing, which in the 1358-1425 timespan that was mentioned had approximately 487,000 people, would have expanded, not shrunk its already larger-than-Tenochtitlan's population by 1519, as the city of Nanjing remains a heavily populated city even today.
The city of Nanjing contained more people during the mentioned timespan than Tenochtitlan had a century later.
Unless you can cite evidence that the city of Nanjing experienced some massive loss of people and a declination of population in the century between the end of the census and 1519, as there is no evidence to suggest otherwise, I would conclude that the population of Nanjing remained higher than that of Tenochtitlan. Especially since the supposed 'height' in population for Tenochtitlan was significantly lower than that of Nanjing a century prior.

Okay then, Nanjing is the most populated city in the world at its time, But did it have Sewers were people spending money at markets? How was the economy?

Now you are moving from population to other matters.
For the record: I am not sure about Nanjing, but Beijing had many canals and was described by Marco Polo to be the 'Venice of the East' or somesuch European comparison [though it is a common comparison]. I am pretty sure, yes, it had sewers.
Beijing had many, many markets. Over seven in the city, I believe. You kind of get that when you rule over the largest population on the planet.
Beijing and Nanjing have traded the position of power in Chinese civilization almost since the dawn of Chinese civilization [though, yes, if I recall correctly, there have been others]. Thus they have been both seats of power and seats of commerace. Nanjing was known for its textiles and Bejing long had a proper place in Silk Road commerace as well as both being important ports. Zheng He, the famous Chinese adrimal, had his home in Nanjing.

Provide evidence that Nanjing was still the largest city in the world at the time.