(Enslaved: Odyssey to the West's fish tank scene occurs at the end of Chapter Two, but in some ways it's worth discovering for yourself, so consider yourself warned if sensitive to spoilers.)
The scene: Monkey and Trip come across something beautiful and incredible. A large fish tank is still thriving after approximately two hundred years in the ruins of New York. Trip explains that it's working as a perfect closed system. The sunlight feeds the plants, the small fish eat the plants, and the big fish eat the small fish.