Remains of a pre-historic henge could be lying just feet below a Lincolnshire field, say experts. Studies of a large site in Navenby, north of Lincoln, have revealed telltale signs of what could be the county's biggest henge. The Bronze age place of ritual, worship or community gatherings is thought to be lying on a strip of land which was later turned into a Roman settlement. Geophysics studies, which are used to detect underground geology and artefacts, have revealed a circular structure.