Author considers geophysical research focusing on localization and recognition of the defensive structures and residential buildings of a the Late Mediaeval motte and bailey earthwork at Zawalów Kolonia in eastern part of Poland. The motte that is the subject of this paper is one of the largest and best surviving of its kind in Poland. In the survey the magnetic method was used with a Geoscan Research fluxgate gradientometer FM 256 with 0.1 nT resolution.