Castell Dinas Brân is a medieval castle, built by the Princes of Powys Fadog, which occupies a prominent hilltop site above the town of Llangollen in Denbighshire, Wales.

[1] The presently visible stone castle was probably built in the 1260s by Gruffydd Maelor II, a prince of Powys Fadog, on the site of several earlier structures, including an Iron Age hillfort.

An earthen rampart - probably with a wooden palisade - surrounded a number of roundhouses and an extra deep ditch was cut to defend the gentler slopes on the southern side of the hill.

In 1879 the pioneering English geologist Charles Lapworth named the Ordovician geological period after the Ordovices as the rock formations he had studied were located in the tribe's former North Welsh domain.

Elisedd, who was a Romano British ruler during the Anglo-Saxon settlement of Britain is named on the Pillar of Eliseg and is considered one of the founders of the Kingdom of Powys, however, no archaeological evidence for any structure from this period has been found.

His son, Madog ap Gruffydd Maelor, the lord of Powys Fadog, who founded Valle Crucis Abbey at Llantysilio in 1201 might have ruled from Dinas Brân.

Dinas Brân was one of several castles being built following the signing of the Treaty of Montgomery which had secured Wales for Llywelyn, free from English interference.

Following the end of the war in October 1282 and the death of Llywelyn, most of Powys Fadog including the castle was granted to John de Warenne, Earl of Surrey.

[7] Castell Dinas Brân has also been a source of inspiration for artists in more recent centuries, such as J. M. W. Turner and Richard Wilson, both of whom strove to capture the castle and its surroundings through their paintings.

The walls on the gentler slopes on the southern and eastern sides are strengthened with an additional 20 feet (6.1 m) deep rock-cut ditch and counterscarp bank.

Its much enlarged windows still look south across the valley and an arched gateway leads from the west end of the room to what was once the Kitchens in the basement of the adjacent apsidal (D-shaped) tower.

[7] Originally, in the enclosed area of the castle there would have been stables, workshops, storage buildings and maybe a chapel but as these were built of wood nothing remains above ground level.

The lyrics were probably inspired by the fourteenth-century love-story of Myfanwy Fychan of Castell Dinas Brân, and the poet Hywel ab Einion.

The tale continues to tell of an arrogant Norman knight, Payn Peveril, who hears that no one has had courage enough to stay overnight inside the castle ruins, for fear of evil spirits.

The giant also tells of a great treasury of idols buried at Dinas Brân which includes swans, peacocks, horses and a huge golden ox but dies without revealing its location.

Due to the exposed steep routes up to the castle, official advice suggests stout walking shoes and warm, waterproof clothing.

Upper junction of the Dinas Brân Formation is likewise not exposed, but opposite the (Llangollen - Panorama Walk) Wern road T-junction at the base of the Eglwyseg Escarpment is a very small outcrop of dark olive-grey mudstone with abundant remains of the brachiopod Dayia navicula (J. de C. Sowerby, 1839).

Silurian fossils can also be observed in scree and rubble below the castle on the steep northern slope and in the deep rock-cut ditches partially surrounding the ruin, which served the dual purpose of both defense and quarrying stone to build Dinas Brân.

Orthocone straight-shelled Nautiloids (Molluscan Class Cephalopoda), various brachiopod species and rare Trilobite remains may also be found.