No visible archaeological features are today associated with Rattin Castle Tower House in County Westmeath,Ireland located near the boundary of the Pale, the area around Dublin and adjoining counties where English control prevailed. However, both magnetic and resistance data show that Rattin Castle was surrounded by a substantial bawn wall, which has since been removed. Interpretation of two-dimensional resistivity shows a deep trench at the site of the bawn wall. A small (12 by 16m) rectangular low-resistance anomaly located outside the northern section of the bawn wall but connected to it, is interpreted as a possible gatehouse providing access to the castle.Less than 20m from this anomaly, the course of an old military road is delineated by magnetic data but is seen most clearly on the resistance data where it is represented by two parallel low-resistance anomalies 230m long. This road is possibly older than the castle.Rattin is associated with an extensive network of subrectangular field boundaries and enclosures,most noticeably west of the castle.The presence of the military road, potential gatehouse, substantial bawn wall and geographical location all suggest that Rattin Castle was an important strategic fortification in Ireland.