Walks were performed in and around the ruins of 'water cities':
Angkor, Cambodia and Machu Picchu, Peru.
Known historically for its intricate canals and water
storage systems, Angkor eventually collapsed
as the result of prolonged drought.
At Machu Picchu an elaborate water system continues
to systematically move water through its canals.
By some accounts the cause of Machu Pucchu's
demise was due to "plagues afflicting the Inca along
with military campaigns waged by conquistadors."
[ livescience.com ]