How about a jungle built inside a city, built inside a jungle. Like a suspended ecosphere. Maybe the jungle outside is dead or dying with horrible creatures or a war torn world and the jungle inside is full of things from our time period. Challanges would be choosing the right camera angle to capture the essence of the outer jungle and inner jungle while also observing the the role of the city and how the inhabitants interact with the enviroment.

Sorry to blurb out like that
Just my crazy brainstorm.

Either way, I like it. Can't wait to see what you come up with.