During the ﬂoods in 2002, the entire lower section of the Prague Zoo was destroyed, including the quarantine block for sick or recently arrived animals. Our assignment was to design a new one. The layout is simple: boxes along a central corridor, from which the caretakers can oversee their charges through a small window in the doors or open the trapdoor into the outside pen. Each group of animals has its speciﬁc requirements for the doors’ opening, their strength, and the safety of animals and zoo workers. The animals must be protected from injury and causing damage, so the heating, for example, is built directly into the cement walls. The building looks almost frighteningly austere, but it is planned to meet all of its complicated functional requirements.