The development of geophysical survey remains a spearhead-priority for new research and cultural resource management alike – since geophysics can find and map sites without destroying them. However, there are current weaknesses of sensitivity and resolution – the instruments cannot easily “see” small features like graves and post-holes of which so many ancient sites are principally composed. Great hopes have been invested in caesium vapour magnetometers, which the Centre for Archaeology has been promoting in England – perhaps nowhere with such dramatic success as at Stanton Drew, Somerset. Here, geophysical techniques have brought to light the lines of broad circles belonging to a previously unrecognised henge monument, and the caesium magnetometer showed these circles to be composed of individual pits about 1.4 m in diameter. The fine focus achieved for these buried features augers well for the discovery and preservation of similar sites and monuments in the future.