A motte is a flat-topped mound built by the normans following the invasion circa. 1170. Its purpose was defensive, to protect against the local people whose land had been seized. It provided a local elevated vantage point from which the surroundings could be viewed. Mottes are often, though not always, associated with a bailey, an enclosed courtyard area that housed animals amd soldiers. There are about 50 such mottes in County Meath with approximately 35 per cent being associated with baileys. Today most mottes in County Meath are grassed over and little information can be obtained about their internal structure. Were they constructed with a core of boulders at their centre, onto which soil was packed, or are they composed mainly of soil, or was a ring of stones first constructed around their base? Archaeological excavations can answer these questions but in the process the motte itself would be destroyed. In this study, two non-invasive, non-destructive geophysical techniques were employed, resistivity and ground-penetrating radar, in order to obtain information about the internal structure of the Galtrim motte.