As I walked among the amazing ruins of Chichen Itza, considered by some to be among the 7 wonders of the world, I pondered that question, and also asked myself what our civilization could learn from them to avoid the same fate.
Our guide showed us the Mayan writing system, one of the few that existed among the world's civilizations at the time.
He also showed us the Mayan numbering system, one of the few at the time that included the concept of zero.
Mathematics and careful observation of their environment allowed the Mayans to build temples so perfectly aligned with the directions of the compass that shadows and light take the shape of a serpent winding down the side of the pyramid on the spring equinox.
The ruins also have amazing acoustics; many of the tour groups clapped together so they could hear the echo that made the call of a Quetzal bird. Here is a video of the acoustics in the ballcourt area (the largest ballcourt in mesoamerica...I couldn't imagine how the players could get the ball through the very high hoops here, especially since they were allowed to use only their hips to hit it).
A big part of the experience is interacting with all the vendors there. Here's what it's like; I took this video as I walked from the observatory through the vendors near there.
Here I am in the area known as the "Plaza of Thousand Pillars".
The "Itza" part of the Chichen Itza name means "sorcerers of water"...perhaps the Mayan people gave themselves that name with pride for how well they managed the water they found in cenotes near there.
But in the end, it was their misuse of natural resources that caused their downfall, in addition to infighting between the various Mayan city-states. Scholars believe their deforestation of the area and the water problems it created made the large city unsustainable...something helpful for us to consider today as well.
It's a huge complex, and I didn't have time to explore it in depth. I hope to visit there again some day.