Development of new city needs comprehensive planning to answer urbanization challenges, such as environmental crises and socio-economic crises. The natural trait of human activities is destroying nature and a city is the most significant place of human activities. Sustainable approaches are important to ensure future's ability to fulfill their needs by regulating today's consumption sustainably. Smart city applications are more than just technology, rather smart city is a way to achieve better city services and offer highest quality of urban life. Therefore, technological usage to achieve sustainability is key for the sustainable smart city concept. This research aims to develop conceptual design based on sustainable smart city concept for Indonesia's New Capital. Conceptual design is developed with urban planning knowledge based on the result of site analysis and case study from other country city's development which later are validated by expert. Initial cost analysis of the conceptual design uses relevant construction cost from benchmark or parametric cost to generate initial cost value. The result of this research is conceptual design that show spatial and usage form with the application of sustainable smart city concept needed for the construction of Indonesia's new capital.