Castle of the Roche Guyon

Description of the castle

1 - Geographical situation

Below Mantes, the Seine runs towards the west; in Rolleboise, it is diverted towards the North-East, forms a vast elbow, returns towards south-west, and thus leaves, on left bank, a peninsula of alluvia of which the length is approximately eight kilometers and the greatest width of four. The throat of this peninsula hardly has but two kilometers of opening. It was a place of excellent camping there, because an army corps, whose right-hand side was supported on Bonnières and the left with Rolleboise, defended without sorrow the entry of the peninsula. But it was necessary to provide that an enemy in forces, by attacking the throat, could, while slipping by along right bank, to try to pass the Seine at the end of the plain of Bonnieres and to thus take the peninsula by its two most distant points. However the right bank, opposite the peninsula of Bonnières, is composed of an escarpment chalky, abrupt, which approaches the Seine with Vétheuil, to leave it with the Rock-Guyon at the top of its elbow. On this point, with the Rock-Guyon, the escarpment is far away from the river only of approximately one hundred meters; formerly it was still brought closer more it, the Seine having moved back its banks.

2 - Description of the site

It is there that at the end of XIe century a castle under excellent conditions was high. Initially a keep very extremely surrounded by a double enclosure was high at the top of the escarpment. Along the river and leaned with the rock which dominates it of much, drew up the castle which cut the road passing on right bank, ordered the course of the river and, consequently, the top of the peninsula. In order to bring closer as much as possible the castle the keep, the chalk escarpment was cut à.pic, so as to leave a rather vast court between the principal building and the foot of the rock. A broad diverted underground, cut in the rock and having the figure of a cylinder with emmarchement, joins together defenses of the castle at the interior court of the keep. Side where the escarpment was less abrupt, was distinct, in the sharp rock, broad and deep ditch à.fond of tank. A less deep ditch, but much wider, circumvented the plate on the end of which the keep sat; but as this plate was not level and than it dominated the keep while being inserted in the chalky chain, one made a factitious mound on which (probably) a defense rose, destroyed today. The natural escarpments were to remove any idea to attack the plate by its sides. We do not think that the ditch and the escarpment were ever protected by walls, but only by one ground lifting with palisades, because it does not remain on these points null trace of masonries.

In order to better do to still include/understand the plate of the castle of the Rock-Guyon, and how, by considerable works, one had managed to make this plate even stronger, either by notching the hill, or by making earthworks, we give a profile of the chalk escarpment with constructions. In A is the Seine, out of B the castle built with the foot of cliff, out of C the keep, of which the enclosures rise while following the angle of rest of the plate to dominate the outside on the side D. In E, the made mound with hand of man, on whom was a advanced work ordering the circumvallation of the plate; the profile of the underground communicating of the castle to the keep is traced in H. One could not enter, of the plate, in the enclosures of the keep that by a postern bored on the side of the courtine external of right-hand side and facing the escarpment, in manner that it was impossible to see this entry either of the plate, or of the bottom of the escarpment Our profile makes include/understand how it was difficult with one besieging to be held in the lower castle without having the higher keep at the same time; if, after having seized the castle, he had wanted to place himself there, he was infallibly crushed by the garrison of the keep.As for seizing the keep, wrapped in his double enclosure, one could try it only by one blockade. But how to block a fortress which had a very practicable underground exit communicating with a ordered lower defense and a broad river? Under the strategic report/ratio, the position of the castle of the Rock-Guyon was thus excellent and obviously selected to keep this peninsula of Bonnière so easy to defend with the throat. Two or three thousand men in the peninsula and four or five hundred men in the castle and its dependences resting mutually, though separated by the Seine, could stop a considerable army and paralyse its movements on one or the other bank of the Seine.

Text of Eugène Viollet le Duc

3 - The keep