Ogmore Castle construction might have begun in 1106. It was in use until the 19th century for a range of purposes, including a court of justice and a prison, but is now a substantial set of remains and a local landmark.
The earthworks were steeply banked and oval in shape, enclosing an area of 50 m in length by 35 m in width. The inner ward was flat and constructed of timber structures. After completion of the ringwork, the building material was stone. The windows were round-headed with Sutton stone ashlar. The first-floor great hall had an ornate fireplace.
William's son Maurice is credited with building the oblong keep; it is perhaps the oldest Norman keep in Glamorgan. Situated north of the main gateway, the keep was the first masonry building and was probably built in the 1120s. It is both the castle's tallest surviving building, and one of the oldest buildings in South Wales. Though only three of the original walls survive, their structure is characterized by irregularly shaped field stones, glacial pebbles, Lias limestone slabs, and brown mortar. Thomas de Londres replaced a timber palisade with a stone wall in around 1200.
In the early 13th century, a second storey was added that housed private apartments. Garderobes were featured on two levels and a latrine tower was part of the exterior. A well-preserved lime kiln was built over an indeterminate 13th-century structure. Subsequently, a courthouse dating to the 14th century and rebuilt in the mid-15th century, was probably the third building to occupy the same spot. The building was rectangular in shape with a simple doorway and was flanked by two chambers. Having sustained damage during Owain Glyndŵr's revolt, a new courthouse, situated in the castle's outer bailey, was built in 1454 and was in use until at least 1631.
The present-day castle remains consist of the keep and some outer walls.
The Castle of Gruyères is one of the most famous in Switzerland. It was built between 1270 and 1282, following the typical square plan of the fortifications in Savoy. It was the property of the Counts of Gruyères until the bankruptcy of the Count Michel in 1554. His creditors the cantons of Fribourg and Bern shared his earldom. From 1555 to 1798 the castle became residence to the bailiffs and then to the prefects sent by Fribourg.
In 1849 the castle was sold to the Bovy and Balland families, who used the castle as their summer residency and restored it. The castle was then bought back by the canton of Fribourg in 1938, made into a museum and opened to the public. Since 1993, a foundation ensures the conservation as well as the highlighting of the building and the art collection.
The castle is the home of three capes of the Order of the Golden Fleece. They were part of the war booty captured by the Swiss Confederates (which included troops from Gruyères) at the Battle of Morat against Charles the Bold, Duke of Burgundy in 1476. As Charles the Bold was celebrating the anniversary of his father's death, one of the capes is a black velvet sacerdotal vestment with Philip the Good's emblem sewn into it.
A collection of landscapes by 19th century artists Jean-Baptiste-Camille Corot, Barthélemy Menn and others are on display in the castle.