Mexico's ancient canal gardens, Xochimilco, once belonged to the powerful Aztec empire.
Fast-forward 500 years, nature resides, along with trash.
"I think we all know that humans caused this, and our way of life," said Andres Castillo Martinez, a conservationist. "Mexico City demands water and the water that we had in these canals came from naturally from the hilly areas. It is a basin."
"The urban stain advances with all that it brings. Contamination of the canals with waste—plastics, glass, organic garbage," added Mr. Martinez.
However, groups of young conservations are helping to clean-up Xochimilco.