The city of Rotterdam must find a way to transition away from natural gas for heating the built environment before 2050. Among the alternatives for future spatial heating is district heating, as residual heat is abundantly available in the Rotterdam harbour. Currently, a small part of the Rotterdam South area is covered by the district heating network (DHN). There is room for expansion of the existing DHN, but the available residual capacity is limited. Also, Rotterdam South has a mixed buildings stock, which could allow for the possibility of exploring a cascaded DHN. However, it is unclear what the future network should look like that fits the criteria of stakeholders best. Twelve possible configurations are tested and evaluated using a minimal cost network model. The objective is to minimize overall network cost and connect all the demand in Rotterdam South. The best configuration is the network where all main collection points are supplied by high temperature heat and where additional capacity is added on top of the existing transport network. The building stock mix in Rotterdam South is not optimal for cascading, which results in higher costs for a connection and a lower overall connectivity.