Château d'Olly, Maison de maître in Olly, Illy, France

The château d'Olly is a manor house built around 1830, probably on the site of an old mill called the Hollier, at the confluence of the Hatrelle and the Givonne. Its long pale stone facade has four levels, with three rows of tall rectangular windows and a lower row of smaller windows. A central projecting bay rises to a steeply pitched roof flanked by tall chimneys, and a squared stone tower with a pyramidal roof adjoins the main block to the right. A lower flat-roofed annex with large metal-framed windows and a red brick base stands to the far right, and a short flight of stone steps with a metal railing leads to the central entrance door.

The house was built around 1830, apparently on the site of an earlier mill called the Hollier. A brickworks operated here first, and its chimney still bears a plaque dated 1858. A spinning mill followed, linked to the Sedan textile trade and served by the CFDA "Bouillonais" railway line through Olly. A fire on 11 July 1908 destroyed the mill annexes, ending the industrial activity and leaving the building as housing.

A tourist plaque in front of the house describes its role as the seat of the Dutch ambulance during the Battle of Sedan in 1870. A memorial stele recalls Jacques Wenzel, a retired gendarme and resistance member who sheltered draft evaders and Allied airmen; he was killed there on 28 August 1944 by francist militia known as la bande au Bossu.

The site lies at the confluence of the Hatrelle and the Givonne in the hamlet of Olly, commune of Illy. The Hatrelle intake channel is disused and partly destroyed by a road, while the Givonne intake still feeds a pond. The château is private and under restoration since 2015; the commemorative stele and tourist plaque stand in front of it.

The property maintains an active water system drawing from the Givonne River that fills a pond and once powered the factories. This river-fed system is a rare example of how nature and industry worked together at this location.