As urbanization accelerates, cities are increasingly challenged to provide adequate infrastructure while addressing environmental impacts and space constraints. This chapter explores the potential of underground infrastructure as a solution to these challenges. By leveraging tunnelling and advanced construction techniques, cities can create new spaces in saturated urban areas, promote sustainable practices, and enhance the resilience of urban environments. This shift towards subterranean development requires a transformation in both social mindset and regulatory frameworks. The chapter also delves into the innovative use of real-time monitoring systems, artificial intelligence, and predictive analytics to optimize maintenance and pre-emptively address issues, heralding a new era in construction. Through an examination of underground infrastructure’s benefits and the necessary policy changes, this chapter outlines a path towards more sustainable and resilient urban development.