The feudal castle was built upon the plan of a triangle, with a tower at each angle, the one at the apex being the donjon.  The form of this lofty keep is rectangular, and the machicolations and embattlements which were added in the fifteenth century are in a perfect state of preservation.  Upon the platform, which I was able to reach by means of ladders and the half-ruinous spiral staircase, viper’s bugloss spread its brilliant blue flowers over the dark stones, and enticed the high-soaring bees.  The view of the wide and beautiful Dordogne Valley from these old battlements was not less grand because more than one-half of the sky was of a bluish-black—­a mysterious canopy that concealed the genius of the storm, but from the turbulent folds of which there darted every minute a dazzling line of light.  The tower on which I stood, although the highest of the three, had never been struck by lightning, but one of the others had been repeatedly struck, and the ruined masonry showed abundant signs of the scorching it had undergone in this way.  Lightning is capricious and incomprehensible in its preferences.

This castle was besieged by Henry Plantagenet in 1159, but without success.  Subsequently he made another effort, and then reduced it.  His son Henry made it his headquarters for some time after he had revolted.  In 1369 Thomas de Walkaffera the English seneschal who held Realville on behalf of his sovereign, was besieged there by a Lord of Castelnau, assisted by other barons.  The garrison was overcome and massacred.  Another Lord of Castelnau, John, Bishop of Cahors, convened a meeting of the States of the Quercy in his fortress, at which a rising against the English was decided upon.  It resulted in their temporary expulsion from the Quercy.

Besides the towers and exterior walls, there are some chambers of the old castle in good preservation.  The chapel is still roofed, and the altar-stone is in its place.  In an elevated chamber at the lower end, the dead were laid while awaiting burial.

Descending to the village, I entered the parish church—­a Gothic building of the fourteenth century, containing many interesting details.  The oak stalls, each with a quaint human figure carved upon it, are exceedingly curious.  Outside the church little girls were playing, in the charge of a Sister who had a beautiful sweet face.  She showed me the way to the next village, where I hoped to find shelter from the gathering storm.  I have a pleasant picture in the mind of Castelnau—­a bowery, ancient, mossy place, with vines climbing about the houses or on trellises in the little steep gardens, and a golden bloom of stonecrop upon the rough walls.