The Galactic Zoo was a zoo which housed Sabre-Toothed Gorillas.
In the Sabre-Toothed Gorilla House of the Galactic Zoo, the Master found "work placements" for a group of Earth colonists for "humanitarian aid", an act he found to be an act of charity. However, the Master had actually fed the colonists to the Sabre-Toothed Gorillas. (PROSE: A letter from the Master)