If you ask people which civilization was the most advanced in building things 2000 years ago, 99% of the people would say the Romans.
But some archaeologists may say the Mayas.
Using LiDAR (Light Radar) the archaeologists recently found a big network of houses, defensive structures, dams, pyramids and other buildings hidden in the jungle of Guatemala.
New estimates now put the number of people living there 2000 years ago at 10 to 15 million, up to 3 times more then former estimates. To feed so many people in the 2100 square kilometer “urban” area, the Maya used 95% of the land for extensive agriculture.
(If the newspaper hasn’t mix something up here, those numbers would mean 5000-6000 people per square kilometer, more dense then a lot of current-day million cities. Berlin for example has only 4000 people per km². Not completely impossible, but incredibly cramped with most of the area fields, not living space.)
They also build an “unbelievable” amount of defensive elements, which indicates that war was normal for them. The same goes for floods in the rain season. The long dams allowed the people to walk to other places and go on with trading, even if everything else was under water.