The fortress of Mornas , in the department of Vaucluse , stands on a rocky outcrop on the left bank of the Rhône , overlooking the village of Mornas , established at its foot and the surrounding area. She had a major importance in the antiquity to the French Revolution , from which it fell into ruin. It was rediscovered in the last third of the xix th century and since 1978 is the subject of many renovations by the Friends of Mornas , heritage conservation association.