The rapid migration from rural to urban areas is leading to overpopulation in cities, posing significant challenges for urban planners. By 2050, it is estimated that 70% of the global population will reside in urban areas. Governments are striving to expand cities to accommodate this growth while preserving green spaces and ensuring a high quality of life. This task is complicated by the limited availability of space. Underground space, often perceived solely as a domain for tunnels, utilities, and mining, offers immense potential for urban environments. This misconception neglects the evolution of underground space into more complex and diverse applications. One innovative application of underground space is shallow geothermal energy schemes utilising abandoned mine workings. This approach offers a low-carbon heating solution crucial for the UK's goal of achieving net-zero emissions by 2050. It is particularly relevant in historical industrial cities with extensive coal mining voids. This study examines the geothermal potential of coalfield mine workings in Greater Leeds, providing a methodology for establishing geothermal energy opportunities in similar geological settings. The insights and methods derived from this study are applicable not only in the UK but also internationally, showcasing the transformative potential of underground space in addressing contemporary urban challenges.