The three-storey, three-bay structure sits on a south-east-facing slope in County Wexford, tucked into a broad col between two ridges, and specialists have suggested it could contain fabric from a house that was already standing four centuries ago. A walled garden lies roughly forty metres to the east, a quiet companion that has outlasted several changes of ownership and at least one violent episode that would have ended the story before it properly began.

The land was granted to William Marwood in 1613, taking the name Castle Marwood in his honour. By 1621 a house of two-and-a-half storeys had been raised, along with a court, a gatehouse, and an orchard. But in 1620, before that building programme was even complete, the Kavanaghs burnt the property. The Kavanaghs were one of the great Gaelic dynasties of Leinster, and the burning likely reflected the wider turbulence of early plantation-era Wexford, where newly granted estates and older Gaelic claims frequently collided. The estate passed to Henry Masterson, who renamed it Moniseede, the name that would eventually settle into its modern form. By 1654, a survey of the 800-acre estate across the Monaseed and Ballylusk townlands recorded a ruined castle and a mill among its features, suggesting that not everything Marwood built had survived intact. The house that stands today, with its projecting return on the north-west side, may preserve something of what was constructed in those early years, though archaeological testing carried out in 2019 produced no material that could confirm a direct physical link to the seventeenth-century structure.