Following the usual configuration of medieval strongholds, Epoisses formed an irregular oval. High walls, flanked by five half-towers, formed a first enclosure that was isolated from the village and the countryside by water-filled ditches.

A single passage gave access to the bailey via a drawbridge. Once past the porch, one found oneself in a real little indoor village. Indeed, the inhabitants of the seigneury who wished to do so built houses in the farmyard which belonged to them and where they settled with their families and their animals in case of imminent danger. They stored their harvests in the granaries of these houses or in those of the castle, out of reach of looters. In exchange for this protection, they were responsible for maintaining the fortifications, each paying the costs according to his or her means; moreover, in case of danger, they had to keep watch and stand guard, an obligation that was not without dispute, especially in peaceful times. These houses were small: one or two rooms, an attic, a room for livestock.

The castle formed a second wall in the western half of the large oval. It formed an irregular octagon, flanked by seven large towers crowned with battlements and linked by curtain walls. Around it, a wide and deep ditch full of water prevented any approach. The inner courtyard was accessed via a drawbridge, which was transformed into a dormant bridge in the 17th century. On the other side of the courtyard, a wooden footbridge, also equipped with a drawbridge, allowed communication with the defences of the first wall. When these drawbridges were raised and the portcullis lowered, the court was inaccessible. There were no openings to the outside, only a few loopholes from which to watch the surroundings and shoot at the attackers.

Inside the courtyard, leaning against the defensive wall, buildings contained, to the south, the kitchen and its outbuildings, a very large cellar where the lord and the villagers kept their wine. Then service rooms: flour room, bread oven, prison. Above, huge granaries housed everyone’s crops. In the towers were the flats of the captain, the public prosecutor and other officers of the lordship. Finally, there was a chapel; the present chapel, which dates from the 17th century, replaced an older building. The buildings to the north, those that survived the revolutionary fury, seem to have always been the home of the lord, his family and his numerous staff. They had large rooms with all the windows facing the courtyard.