An underground station for the measurement of low-level radioactivity is in operation in Northern Italy in the town of Como under the Baradello hill. The rock cover is -300 m water equivalent. This paper reports about the preliminary measurements carried out to characterise the site of the Baradello hill and the installation of a high-purity Ge detector with a radio-pure copper shielding. Features and levels of the achieved background are reported and discussed, in comparison with other above ground and underground low-radioactivity stations. Sensitivities to radioactivity in typical environmental matrices are evaluated, confirming the very low-gamma background attained in the laboratory.