Bryn Celli Ddu (Welsh pronunciation: [ˌbrɪn kɛɬi ˈðɨː]) is a prehistoric site on Anglesey, a Welsh island near Llanddaniel Fab. Its name means "the mound in the dark grove." It was excavated by archaeologists between 1928 and 1929. Visitors can enter the mound through a stone passage to reach the burial chamber. The site is the main feature of a major Neolithic Scheduled Monument protected by Cadw. A mysterious pillar inside the burial chamber, a copy of the 'Pattern Stone' carved with curved and winding designs, and the fact that the site was once a henge with a stone circle have drawn much interest. The site may have been used to help determine when the summer solstice occurs.
The monument
Bryn Celli Ddu is widely seen as one of the best-preserved passage tombs in Wales. Its passage and burial chamber remain intact, and the structure is still covered by a mound or cairn, which was rebuilt after it was excavated in 1929. Many other stone chambered cairns have lost similar features. Today, the passage is 8.4 meters (28 feet) long, with the first 3.4 meters (11 feet) uncovered and marked by two large stones called portal stones. The main passage has walls made of vertical rock slabs, with a roof formed by flat stones called lintels. The mound is now smaller than it originally was and no longer fully covers the burial chamber. This allows the back wall to be exposed to air, letting in some natural light.
Inside the burial chamber, there is a smooth pillar made of blueschist, a type of rock that formed under high pressure and heat. The pillar is about 2 meters (6.6 feet) tall and has a rounded shape.
Behind the back wall of the chamber, in an area that was once inside the mound, there is a replica of the "Pattern Stone." This stone was found buried under the mound and has been placed upright in what is believed to be its original position when the site was a henge, not a tomb. The stone has curved, snake-like patterns on both sides. Another stone inside the tomb has a small spiral carved into it, though its true origin is uncertain.
Outside the tomb, a circle of large stones called kerbstones marks the original size of the mound. These stones also follow the path of a ditch from an earlier henge monument. Three stones inside the cairn are thought to have come from the stone circle of that earlier time.
The passage is aligned with the sunrise on the Summer Solstice. For several weeks around this time, sunlight can enter the passage and reach the back wall of the burial chamber.
The monument is part of a group of ancient sites from the Neolithic and Bronze Age periods. Two other cairns have been found just to the south of Bryn Celli Ddu. To the west, there is a standing stone and a rock formation with carved cup-shaped marks.
Original uses
The earliest remains found at the site are a row of five postholes, which were once believed to be from the same time as the tomb. Tests on pine charcoal from two of the pits, done in 2006, showed they are about 4000 BC, near the end of the Mesolithic period, 1,000 years before the next stage of the site's use. However, the purpose of these postholes is still unknown.
Around 3000 BC, a henge monument was built. This structure would have had an outer circular bank and ditch to mark its boundary, though only the ditch remains today, measuring about 21 meters (69 feet) wide. Inside the ditch, a circle of 17 stones would have formed an oval shape, with many stones arranged in pairs on either side of the center. Some of these stones had cremated human remains buried at their bases, suggesting the presence of a central "altar." During this time, a pit was dug inside the henge. A single human ear bone was buried there and covered with a flat stone. Nearby, a second stone called "The Pattern Stone" was found, showing serpentine patterns on both sides. It is believed this stone would have stood upright within the henge.
About 1,000 years after the henge was built, the site was changed significantly. Almost all of the standing stones were deliberately damaged, with some knocked over and six broken using heavy stones. In their place, a passage grave was constructed. This structure would have been much larger than the mound that remains today, with a full circle of kerbstones following the line of the old henge ditch to form a large retaining wall around the mound, which would have been about 26 meters (85 feet) wide. The burial chamber would have been completely enclosed within the mound, unlike the reconstructed mound seen today, which has an open back wall. Human bones, both burned and unburned, were found inside the chamber and passage, showing a mix of burial practices. In all cases, the tomb was reused, and old remains were removed.
At the end of its use, the tomb was sealed by placing a large stone across the entrance, positioned between the two portal stones.
Archaeology
The earliest descriptions of the site date back to around 1800. In 1796, it was listed among Anglesey cromlechs in the Cambrian Register. In 1802, John Skinner wrote about his visit to the Isle of Anglesea in a book called "Ten Days' Tour Through the Isle of Anglesea," which was not published until 1908 as part of Archaeologia Cambrensis. During his visit to Bryn Celli Ddu, Skinner learned that the passage tomb had been found about a generation earlier by a farmer searching for usable stone. The farmer was initially frightened by the sight of the pillar stone but returned after hoping to find treasure and removed it.
By 1928–1929, Wilfrid Hemp studied the site and uncovered the history of its use. He discovered the 'Pattern Stone,' which was later moved to the National Museum of Wales. A replica now stands near the original location, close to the mound. The pillar was placed upright again, and the earth and stone covering the passage and chamber were restored. However, fewer materials were available than originally used, and some concrete supports were added later.
In 1906, Norman Lockyer wrote the first detailed study about megalithic astronomy and suggested that Bryn Celli Ddu aligned with the summer solstice. This idea was not widely accepted at the time. However, research by Christopher Knight and Robert Lomas in 1997–1998 confirmed the alignment. They also found that the site could be used as an agricultural calendar. Steve Burrow, a Neolithic archaeology expert, later supported the summer solstice alignment. This connection links Bryn Celli Ddu to other sites, such as Maes Howe in Orkney and Newgrange in Ireland, which align with the winter solstice. Some researchers believe a feature similar to Newgrange’s 'lightbox' may also exist at Bryn Celli Ddu.
Between 2015 and 2020, the 'Bryn Celli Ddu Public Archaeology Project' studied the area around the site. This project, led by Cadw and Manchester Metropolitan University, involved local communities in archaeological work. Researchers examined ancient rock art on nearby rocks and discovered other rocks with 'cup mark' carvings. A second burial chamber, located 50 meters south of the main one, had been destroyed. However, a 2019 excavation found a large circular burial cairn, which carbon dating placed at 1900 BC. This is over 1,000 years after the original passage grave was built.
Media
The serpentine pattern and the passage tomb were important parts of the short animated film Songs from Stones, which highlighted some of Anglesey's meaningful archaeological sites and artefacts. The film was made as part of the Cultural Olympiad in 2012.
The HeritageTogether project used photogrammetry to make 3D models of the site and the standing stone.
Media company Mint Motion created an animated video showing the site's development over time and a flythrough of a pointcloud model of the site (see external links below).
The site was shown and examined in an episode of the US reality television series Expedition Unknown.
Modern history
The site is used by the Anglesey Druid Order for ceremonies that celebrate eight pagan festivals throughout the year, such as the summer and winter solstices.