As I look around, I see causeways, stair-stepped temples, feathered headdresses, and a busy city.

What civilization have I found?

new orleans or rio most likely rio

Explanation:

new orleans has causeways, im not sure about temples, and during mardi gras parades they do elaborate feathered head dresses and its very busy

rio is more all year round with the headdresses it has temples and very busy