Wiston must rank as one of the best-preserved motte and bailey castles in Wales. It was named after an early Flemish settler named Wizo, many of whom were brought to the area by Henry II. Although Wizo died by 1130, the castle is mentioned in 1147 when it was taken by the Welsh. It changed hands many times and whilst William Marshal the Elder does not seem to have taken much interest in the site, his son, William the Younger was ordered by Henry III to rebuild the castle during his time as Earl of Pembroke with the assistance of his knights and local free men.
However, the castle seems to have been abandoned abruptly in late 1220 with no additional building work being carried out at the site. However, the polygonal shell keep probably dates from the early 13th century, and could be the work of William the younger. Archaeological excavations have shown that there were two phases of rebuilding in the interior of the keep, and the finds made during the work suggest it was occupied into the 14th century.
In the 18th century, the motte was included into the parkland as a picturesque feature ringed by a group of sweet chestnut trees, of which a few ancient examples survive.