SOME of the earliest Iron Age defences at Edinburgh Castle have been unearthed during excavation work for the attraction's new visitor centre.
Archaeologists discovered two huge, 2000-year-old ditches underneath the Castle Esplanade, which would once have protected the ancient hill fort on the site.
A team of experts drilled a series of small bore holes through the Castle's car park and analysed soil samples from many metres below the ground.
Senior archaeologists today described the find as a "major discovery" that would help show how the Castle has developed since being established by Iron Age tribes.
It comes just months after the same team discovered the foundations of a 17th-century stone wall, built after the Castle was seized by Oliver Cromwell.
Peter Yeoman, senior archaeologist at Historic Scotland, said: "The results from the archaeological boring were really surprising as this technique rarely produces detailed dating evidence. The data is truly invaluable as it adds another piece to the lost history of Edinburgh Castle.
"These discoveries will help us to understand how the Castle developed over the years. We had some idea about the ditches before we started the excavations, but now we know exactly how big they were and where they were.
"We can now be certain that the front of the Castle was encircled by a pair of massive ditches dating as far back as the Iron Age, 2000 years ago. Each ditch was about 12 metres wide and six metres deep and they were slowly filled in with soil and other debris throughout history.
"The boring has discovered that, within these now in-filled ditches, there are layers and layers of fascinating historical remains - such as 12th and 13th-century pottery.
"We ended up with samples that covered around 1500 years of history leading up to the 1600s, when the whole facade of the Castle changed into its current format."
A special drilling rig was used to recover the samples, which were taken to Headland Archaeology's laboratory in Leith.
Headland's environmental archaeologists were then able to recover dateable pottery fragments and food debris.
Chris Watkins, head of major projects at Historic Scotland, said: "It is always very exciting when a project such as this leads to the discovery of more information on the history of Edinburgh Castle.
"Most of the underground work on the project, including the 26m deep piles to support the new terrace, is now complete and we are progressing with the building of new stonework and the development of the website."
Previous archeological excavations at the Castle have found remains dating back as far as the late Bronze Age from around 900BC.
The Votadini tribe inhabited the Lothians region during the late Iron Age period, around the time of the birth of Christ.
They built hill fort defences which are still visible on Arthur's Seat, at Dunsapie Hill and above Samson's Ribs.
They are likely to have been centres of powers for the Votadini, who also referred to their hill fort on Edinburgh castle crag in an ancient poem.
Traprain Law in East Lothian was one of the tribe's major settlements, with excavations showing it covered around 40 acres.
It was already being used as a burial place as early as 1500BC, and there is evidence of occupation and ramparts from after 1000BC.
Excavations in the 1980s discovered signs of habitation from the first and second centuries, including Roman pottery, bronzes and brooches, which may show a trading relationship with the Votadini.
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