Entrance to a neolithic passage tomb circa 2000 BC Ynys Môn. The Greek geographer Strabo wrote in late first century BC and early first century AD of a holy island where priestesses dwelled. Many Irish myths speak of sacred islands to the west. Early Celtic Christian saints were also often connected with such places. The island of Ynys Mon, called Anglesey Mona Insulis by the Romans, was an ideal location for a sanctuary of druids and tribes.

An island off the northwest coast of Wales, Ynys Môn was also known as Mam Cymru or "Mother of Wales" because of its fertile farmlands, abundant streams and lush forests. It was also rich in copper ore, which provided material for jewelry as well as weapons. Nearby are the beautiful peaks of the Snowdonia Mountains and the tidal Menai Strait. This area has been populated since 7000 BC. Evidence of the different people who lived on this isle can still be seen in the many remains of hillforts, standing stones and burial mounds, each of which has their own story to tell.

Some of the most important relics from Ynys Môn's past have survived from the period just prior to the Roman occupation, second century BC to first century AD. A hoard was discovered in a bog near the lake by Llyn Cerrig Bach. About 150 items including pieces of chariots, many iron spearheads and other weapons, cauldrons, shields, slave chains, bronze ornaments, and even a bronze war trumpet were found in a site where votive offerings were thrown down into the water from the nearby cliff. Judging from the quality of these treasures, they once belonged to high-ranking members of the community. The fact that the craftsmanship of some of these objects can be traced to faraway places proves that Ynys Môn was an important center for trade as well as religious ceremonies.

Tacitus wrote a graphic account of a battle on the shores of Menai Bay in 60 AD between the legions of Roman General Suetonius Paulinus and the Druids of Ynys Mon. These Druids were at the core of the native tribal resistance against the Romans. Paulinus was set on annihilating the sanctuary and everyone in it, thus clearing the way for Roman rule in Wales. The fight was bloody and vicious.

"By the shore stood an opposing battle-line, thick with men and weapons, woman running between them, like the Furies in their funereal clothes, their hair flowing, carrying torches; and Druids among them, pouring out frightful curses with their hands raised high to the heavens, our soldiers being so scared by the unfamiliar sight that their limbs were paralysed, and they stood motionless and exposed to be wounded."

The battle ended with the sacred grove desecrated and totally destroyed. Perhaps this is why so many precious objects were thrown into the lake, as offerings to appease the local gods after the massacre by the Romans. Not long after the destruction of the druid stronghold, Paulinus moved on to Britain to strike another powerful blow against the native British tribes by defeating Boudicca.