Formerly a tidal island, Cornet Rock was first fortified as a castle between 1206 and 1256, following the division of the Duchy of Normandy in 1204. In 1339 when a French force captured the island and occupied it for several years, Cornet was besieged and captured, and the garrison massacred. With the advent of cannon and gunpowder, the castle was remodelled between 1545 and 1548. Prof. John Le Patourel, in The Building of Castle Cornet mentions that in 1566, iron and hammers were taken to 'Creavissham' (i.e. Crevichon), and that island quarried for the castle.
Castle Cornet served as official residence of the Governor of Guernsey until 1672 when the keep was catastrophically destroyed. A bolt of lightning struck the magazine of the castle, destroying the keep and a number of living quarters. The Governor at the time was Lord Hatton. His mother, wife and a number of members of staff were killed in the explosion. It became integrated into the breakwater after the period of the Napoleonic Wars. Along the breakwater, a pond for toy yachts was constructed in 1887 for Queen Victoria's Diamond Jubilee, which served as a seaplane base during World War I. In World War II, it became occupied by a small group of German troops. It was presented to the people of Guernsey in 1945 by the Crown.
The castle incorporates today several museums, like castle museum, maritime museum and Royal Guernsey Militia museum.
References:Trenčín Castle is relatively large renovated castle, towering on a steep limestone cliff directly above the city of Trenčín. It is a dominant feature not only of Trenčín, but also of the entire Považie region. The castle is a national monument.
History of the castle cliff dates back to the Roman Empire, what is proved by the inscription on the castle cliff proclaiming the victory of Roman legion against Germans in the year 179.
Today’s castle was probably built on the hill-fort. The first proven building on the hill was the Great Moravian rotunda from the 9th century and later there was a stone residential tower, which served to protect the Kingdom of Hungary and the western border. In the late 13th century the castle became a property of Palatine Matúš Csák, who became Mr. of Váh and Tatras.
Matúš Csák of Trenčín built a tower, still known as Matthew’s, which is a dominant determinant of the whole building.