Raglan castle is a fortress begun in the 15th century by William ap Thomas, a Welsh lord with political acumen. He married two different heiresses in succession, which garnered him great wealth and position within the society of the day.

Likely the original construction at Raglan took place in the early 11th century as part of the initial conquest of south Wales by William Fitz Osbern, the Earl of Hereford. If so, little trace remains today except for possible remains of a bailey ditch. The site was occupied as a manor from the twelfth century until William ap Thomas bought it in the 15th and turned it once again into a castle.

Raglan has been described as one of the last formidable displays of medieval defensive architecture. much of what survives that was built by William’s son, also named William. The castle is approached through a gatehouse and bridge leading to an initial court. The great hall and domestic buildings separate the first court from a second, which has its own external gate and bridge. The centerpiece of the castle is the hexagonal great tower, protected by its own moat. It was once three stories high and was designed to have its own water and food supplies in the event of a siege.

William was executed for treason having supported the Yorkest cause. The family continued to prosper however up until the English civil war when they supported the royalist cause. At that point the castle was surrendered after a siege and slighted.

Raglan is also home to the first water-commanding engine, a water cannon, designed by a 17th century owner of the castle.