Giraud-Sannier, an architect from the Boulonnais, erected Rosamel Castle in 1770, on the basis of the medieval castle plan.

The castle is divided into four parts, composing a compact square, with a courtyard inside. Three sides are bordered with moats. A cylindric tower is erected at each of the four corners. The southern façade is opened on the main courtyard. This entrance façade is divided into five parts, including one slightly ahead the others, with a pediment above, showing the symbols of Amiral Rosamel.

On each side of the main courtyard are the outbuildings, built symmetrically, in the same style than the castle, with a gorgeous chapel still remaining. The castle and outbuildings façades and roofs, as well as the moats, are registered in the Inventaire Supplémentaire des Monuments Historiques (French list of historical buildings to be protected), 1913 law.

From the garden, only separating walls and some pavilions partly ruined still remain today. An historical description says: “At the southern side of the main courtyard, decorated with two sober lawn pieces, then come the fence and a green lawned perspective bordered with rows of trees, which, obviously, should have created an entrance avenue. However, the historical entrance, by the farm courtyard, has been kept, with only lawn pieces around it, prolongated by the wide Fayel Avenue, totally lawned between its three rows of trees. Right at the exit of the farm courtyard, just after a canalized river has been crossed, one can see two symmetrical oblique lanes, one going to the meadows, the other to the village. On the river edges are some Carpinus, built into pergolas. A wide parallel canal is also there.

At the East, from the dining room windows, one is above an elegant mixed-border, from which classical buxus have been prohibited. It is composed of lawn and flower- beds in the Neufforge style, and is ended by a semi-circular shapes below two terraces with sustaining walls.Then comes the wood, propagating on the stiff side of the slope, crossed by a wide central lane, with a green carpet, perpendicularly to the castle, with also oblique and symmetrical lanes, offering views on the landscape.