By 1573, Château Gaillard was uninhabited and in a ruinous state, but it was still believed that the castle posed a threat to the local population if it was repaired. Therefore, at the request of the French States-General, King Henry IV ordered the demolition of Château Gaillard in 1599. Some of the building material was reused by Capuchin monks who were granted permission to use the stone for maintaining their monasteries. In 1611, the demolition of Château Gaillard came to an end. The site was left as a ruin, and in 1862 was classified as a "monument historique". In 1962, a conference on the contributions of the Normans to medieval military architecture was held at Les Andelys. Allen Brown attended the conference and remarked that the castle was "in satisfying receipt of skilful care and attention". The journal "Château Gaillard: Études de Castellogie Médiévale", which was published as a result of the conference, has since run to 23 volumes, based on international conferences on the subject of castles. In the 1990s, archaeological excavations were carried out at Château Gaillard. The excavations investigated the north of the fortress, searching for an entrance postulated by architect Eugène Viollet-le-Duc, but no such entrance was found. However, the excavation did reveal was that there was an addition to the north of the castle to enable the use of guns. Typologically, the structure has been dated to the 16th century. The conclusion of the excavations was that the site had "enormous archaeological potential", but that there were still unanswered questions about the castle. After Philip II took Chateau Gaillard, he repaired the collapsed tower of the outer bailey that had been used to gain access to the castle. The archaeological investigation examined the tower generally thought to be the one collapsed by Philip, and although it did not recover any dating evidence, the consensus is that he completely rebuilt the tower. In conjunction with the archaeological work, efforts were made to preserve the remaining structures. Today, Château Gaillard's inner bailey is open to the public from March to November, while the outer baileys are open all year round.