A modular shelter pod and system are described herein. In one example, a pod may be formed by a number of foldable or detachable panels, where a first panel includes at least four cavities at first locations having a first shape and a first cross section. A second panel may include at least four tabs at second locations corresponding to the first locations, and having a second shape and a second cross section that fits into and engages the at least four first cavities, such that the at least four tabs engage the at least four cavities to resist movement between different pods when arranged vertically. The pod may additionally include a third panel removably connecting the first panel and the second panel and forming an opening defining a cleaning port that is sealable, where the cleaning port is shaped to removably engage a cleaning device.