Conisbrough Castle was once the principle northern stronghold of the de Warenne Earls of Surrey, who held the lands of Conisbrough from 1069 until 1347. Willam the first Earl built a timber motte and bailey castle on the site during the early-10705.- By the time of the fifth Earl, Hamelin Plantagenet, the wooden castle was no longer adequate to demonstrate the wealth and power of one of medieval England's most influential families. In 1180 Hamelin ordered the construction of a stone Keep (Donjon) to a new design. The Keep, which is circular in plan, is supported by six buttresses and stands to a height of 27 meters. Following the demise of the Warenne family the Castle rapidly lost its importance, and by the end of the 1400s had been abandoned as a residence. The Castle fell into disrepair, ironically this saved it from destruction during the English Civil War of the 1640s, as it was by that time militarily indefensible. In 1994, following five centuries of neglect, two new floors and a roof were placed into the Castle Keep, protecting it from the elements for generations to come. Today, Conisbrough Castle's Keep is considered to be one of the finest examples of medieval architecture in Europe.