The Animal Shelter is a building that appears in the episode "Plankton's Pet." This is where Plankton picks out Spot as his newest pet. Also, it is revealed that SpongeBob got Gary from the Animal Shelter as well.
The outside of the Animal Shelter has a pretty rough design being made of metal. It also has barbed wire at the very top and the words "Animal Shelter" written in the middle.
The inside of the Animal Shelter resembles almost the inside of a prison. It has many cages that keeps the animals locked away in.