What remains at Slanestown, on a gently undulating stretch of Westmeath pasture, is roughly an arc, the western and southern sweep of what was once a subcircular earthwork enclosure some 37 to 39 metres across. The eastern half has been levelled, and a modern field fence now cuts across the perimeter where the outer bank and fosse, the defensive ditch that would have run between the two banks, were removed. The surviving arc still carries a low bank of earth and stone, and to the west-northwest a deep fosse and outer bank remain legible in the ground. Old cultivation ridges run through the surrounding field, and a scatter of roughly circular depressions nearby may point to past quarrying. From the air, the site resolves into a cropmark, the buried footprint of the enclosure showing faintly as differential growth in the grass above.

A rath is the commonest monument type in the Irish landscape, a circular or subcircular earthen enclosure typically dating to the early medieval period, roughly the fifth to twelfth centuries, and used as a farmstead by a single family or household. Most were defined by a bank, a fosse, and sometimes one or more outer banks, the arrangement here at Slanestown suggesting a reasonably substantial example. The site appears on the 1837 Ordnance Survey six-inch map as a complete subcircular earthwork, its dimensions clearly readable. By the time the revised twenty-five-inch map was produced in 1913, the record had already shifted, with only an arc of scarp indicated from the southwest round to the west-northwest. A description from 1980 confirmed what the maps had begun to show: the enclosure survives on its western and southern sides, but has been lost entirely to the east, north, and northeast. The interior slopes gently to face east, which would have made practical sense for any original settlement, catching morning light and offering reasonable drainage.