Within an Inch of His Life by Emile Gaboriau

The prison of Sauveterre is in the castle at the upper end of town, in a poor and almost deserted suburb. This castle, once upon a time of great importance, had been dismantled at the time of the siege of Rochelle; and all that remains are a few badly-repaired ruins, ramparts with fosses that have been filled up, a gate surmounted by a small belfry, a chapel converted into a magazine, and finally two huge towers connected by an immense building, the lower rooms in which are vaulted.

Nothing can be more mournful than these ruins, enclosed within an ivy-covered wall; and nothing would indicate the use that is made of them, except the sentinel which stands day and night at the gate. Ancient elm-trees overshadow the vast courts; and on the old walls, as well as in every crevice, there grow and bloom enough flowers to rejoice a hundred prisoners. But this romantic prison is without prisoners.