CAIRO, EGYPT - December 17: A pig has a standoff with a cow on December 17, 2014 in Cairo, Egypt. Nestled under the cliff of Mokattam is Manshiyat Naser, or Garbage City. Pigs were slaughtered in mass by the government a few years ago but their population has returned. It is a majority christian neighborhood with an economy built on waste collection and recycling. Families divide responsibility from collecting trash, sorting it, processing it, and either selling it to outside factories or processing it into final goods. (Photo by David Degner/Getty Images).