The Fogg Dam nature reserve is about 100km outside of Darwin. It was created back in the 1950s as an experimental rice growing project. The project failed for a number of reason, but not least among them was the migratory birds that came and ate all the rice. Eventually they just gave the place over to the birds and turned it into a nature reserve. It’s now one of the best places in the Northern Territory for bird watching. Of course this is a picture of trees, not birds, so sorry if I led you on.
On another note, the dam is actually more of a low dike and in places it’s not all that obvious of a structure, even when you’re standing on it. (I was standing on it when I took this photo.) It is actually recommended that you don’t walk along it due to the possible presence of crocodiles.