One of Anglesey’s most famous prehistoric landmarks, Bryn Celli Ddu (the ‘Mound in the Dark Grove’ in English) is actually two sites in one. In the early Neolithic (New Stone Age) period, a henge (bank and ditch) enclosing a circle of stones was built here, to be replaced later by a chambered tomb beneath a mound measuring up to 85ft/26m in diameter. Inside, a long, narrow passage leads to an octagonal chamber 8ft/2.4m across, where artefacts such as human bones, arrowheads and carved stones have been found. But Bryn Celli Ddu’s most unusual feature can only be seen once a year. As the sun rises on the summer solstice (the longest day of the year) shafts of light shine directly down the tomb’s passageway to illuminate the chamber within. https://cadw.gov.wales/visit/places-to-visit/bryn-celli-ddu-burial-chamber

Established nearly two millennia ago, this strategically-placed fort at the edge of the Roman Empire bustled with life for more than three hundred years. Segontium was founded by Agricola in AD77 after he brutally suppressed a rebellion by the native tribe known as the Ordovices. Designed to hold a 1,000-strong regiment of auxiliary infantrymen, it was linked by Roman roads to the main legionary bases at Chester and Caerleon. Thanks to excavated coins we know the Romans stayed until about AD394 – no other fort in Wales was held so long. Segontium not only controlled access to fertile and mineral-rich Anglesey but later helped defend the Welsh coast against Irish pirates. https://cadw.gov.wales/visit/places-to-visit/segontium-roman-fort