El HoumaEl Houma is a socio-cultural urban concept in Algiers that represents urban lifeUrbanlife and the space that facilities it, and it is considered in this chapter, as an emblematic case to study architectural exaptationExaptation at the urban scale. Exaptation was used in this chapter, to understand the relationship between design elements and social activities, while the concept of redundancyRedundancy highlights how various structures and elements can promote rich and diverse urban life. In this respect, El Houma as a case studyCase studies was utilised to illustrate how people use and transform the meaning of urban spacesUrbanspace, in the city of Algiers, in an unexpected, spontaneous, and creative manner. Some of the activities mentioned in this chapter can be considered informal by the global literature, whereas this chapter attempts to address the prejudices that paint urban informalityUrbaninformality as a state of deregulation and investigates its contribution to the resilience of the urban fabricUrbanfabric and the community. The chapter reports on the findings of a fieldwork carried out in three neighbourhoods in Algiers and of a comparative analysis of deterministic and indeterministic designs and their influence on urban life as a measure of Exaptation of the built environmentBuilt environment. This research concludes that the intense El HoumaEl Houma is the more enjoyable city life is, and urban fabricUrbanfabric is more resilient when and where it is more possible to have a variabilityVariability of forms, spaces, and redundancyRedundancy of structures.