Richard fixed its site where the Seine bends suddenly at Gaillon in a great semicircle to the north, and where the valley of Les Andelys breaks the line of the chalk cliffs along its banks.

Blue masses of woodland crown the distant hills; within the river curve lies a dull reach of flat meadow, round which the Seine, broken with green islets and dappled with the grey and blue of the sky, flashes like a silver bow on its way to Rouen.

The castle formed part of an entrenched camp which Richard designed to cover his Norman capital.

Approach by the river was blocked by a stockade and a bridge of boats, by a fort on the islet in mid stream, and by a fortified town which the king built in the valley of the Gambon, then an impassable marsh.

In the angle between this valley and the Seine, on a spur of the chalk hills which only a narrow neck of land connects with the general plateau, rose at the height of three hundred feet above the river the crowning fortress of the whole.