We present a new type of gaseous detectors, the spherical proportional counter. It consists of a small metallic ball, 16 mm in diameter, located at the centre of curvature of a large spherical vessel, acting as a proportional amplification structure. It allows high gas gains to be reached and operates from low to high gas pressure. This simple and robust structure allows large volumes to be read out with a single electronic channel. The detector performance presently achieved is already close to fulfil the demands of many challenging projects from low energy neutrino physics to dark matter detection with applications in neutron, alpha, gamma spectroscopy. Preliminary results of neutron flux measurements currently going on in underground laboratory will be presented.