Supply of cool air during the summer period in open areas is utilised to improve human thermal comfort by the urban microclimate improvement of populated spaces. The aim of the chapter is to study the implementation of earth cooling techniques, in open spaces, that mitigate heat in a city’s scale. Details of the earth’s thermal inertia in contact with the atmosphere will be analysed together with the basic underground technologies, e.g. underground heat exchange tubes for external environment improvement. Boundary conditions, the basic equations that describe the heat transfer and air movement and simulation tools that handle microclimatic effects due to earth cooling will also be discussed. Practical information related to sizing and construction of these systems will be tackled. The chapter concludes by presenting examples of application of these systems at outdoor spaces.