The green mounds in the castle gardens were once the site of one of the strongest and most important castles in England. The building of the castle began in 1067 on the direct instructions of William the Conqueror who had crossed the River Thames at Wallingford on his way to London to take the throne.
The castle was expanded in the 13th century after which it became a royal castle, closely associated with many medieval kings.
In 1502 the castle was inherited by the future Henry VIII, but he preferred his manor house at nearby Ewelme. The castle fell into disrepair and was robbed of stone and lead which was shipped down-river to help with building work at Windsor.
In the 17th century Wallingford Castle enjoyed a renewed and final glory. During the Civil War it was refortified as a Royalist stronghold but, realising its potential danger to their cause, Cromwell's Council of State ordered its demolition on 17 November 1652.
The site is now a garden offering the visitor a peaceful stroll and a place for rest and contemplation. The flower beds are designed to maintain a kaleidoscope of colour throughout the summer season and the work by the Council's parks staff has been recognised by the presentation of the Britain in Bloom award. A wild life area has been carefully developed over the past few years and includes wild flowers and plants that are (or were) indigenous to this area of the Thames Valley. These flowers have also encouraged recolonisation of the area by many butterflies.