What’s Buried Under Edinburgh Castle?

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Edinburgh Castle stands proud on its ancient volcanic plug, commanding the skyline like it always has. But the real drama isn’t up top — it’s happening deep below your feet. Beneath the cobblestones and cannon emplacements lies a layered world that spans nearly three thousand years of human story: Iron Age settlers, medieval kings, pirate prisoners, royal treasures, and legends that refuse to die. Pull back the stone and here’s what you’ll find.

Secrets, skeletons, and Scotland’s oldest stories lie beneath the stone.

A Rock Older Than History Itself

Castle Rock is no ordinary lump of geology. It’s the solidified core of a volcano that erupted around 340 million years ago — one of the oldest geological features you can stand on in Scotland. Long before any castle existed, Iron Age communities recognised its defensive potential and built a hill fort here. When archaeologists dug beneath the rock during construction of the castle’s service tunnel in the late 1980s, they found something extraordinary: evidence of human settlement dating back to 900 BC. That pushed back the known history of habitation on this site by a full 1,500 years. They also uncovered traces of Roman Iron Age huts from the 1st and 2nd centuries AD, and an early medieval midden radiocarbon dated to around AD 449–598 — complete with a decorated bone comb of Anglian or Pictish form. This is one of the oldest continuously inhabited places in Scotland, and most visitors walk right over it without a second thought.

The Lost Tower of King David II

One of the most extraordinary archaeological discoveries beneath the castle was made by accident. In 1912, architect W.T. Oldrieve was inspecting a coal cellar when he noticed an ancient window embedded in the wall. Curious, he began digging — and kept going. Five metres down, he broke through a stone vault and found himself staring at the worn steps and original front doorway of a building that had been lost to history for over three centuries.

This was David’s Tower — a mighty royal residence commissioned in 1367 by King David II, son of Robert the Bruce. Standing 30 metres high, it dominated the medieval Edinburgh skyline and served as both the king’s lodgings and a secure vault for royal treasures. Its walls, almost three metres thick, still rise 12 metres inside the rock to this day. The tower met its end during the Lang Siege of 1571–73, when English cannon destroyed it. Its rubble was sealed inside the new Half Moon Battery — entombing David’s Tower beneath the castle’s most iconic defensive wall for centuries. Inside the ruins, archaeologists found cannonballs, iron shells, coins from the reign of Edward I, glass wine flagons, and pottery. The tower also contained the great hall believed to be the site of the infamous Black Dinner of 1440, when the young Earl of Douglas and his brother were murdered in front of the boy king James II.

Dungeons, Prisoners, and Stories Scratched in Stone

Beneath Crown Square lies a labyrinth of stone vaults, the earliest sections dating from the late 14th century. Over the centuries they served as pit-prisons, storehouses, kitchens, and bakeries — but it’s their role as a prison that left the most vivid mark.

In 1720, a group of 20 pirates captured off the west coast of Scotland with a ship’s hold full of gold were brought here and imprisoned. Most were subsequently hanged below the high water mark at Leith. During the wars of the 18th and 19th centuries — the Seven Years’ War, the American War of Independence, the Napoleonic Wars — the vaults were crammed with up to 1,000 captured prisoners at a time, from France, Spain, the Netherlands, Ireland, Italy, Denmark, and Poland. Conditions were notoriously harsh: cramped, damp, and poorly ventilated. But the prisoners left their mark. Carved into the old wooden doors are names, dates, and drawings — including an early version of the Stars and Stripes flag, etched there by American prisoners. These marks remain to this day. The vaults weren’t only used in the distant past, either: in 1916, socialist John MacLean was held here, followed in 1917 by trade unionist David Kirkwood — both imprisoned without trial.

Women were imprisoned here too. Following the Jacobite Rising of 1745, Jean Cameron of Glendessary — who had raised 250 soldiers to fight for Bonnie Prince Charlie — was held in the castle. Lady Margaret Ogilvy made her own escape, disguised as a laundry maid, later joining her husband abroad.

Royal Treasures Hidden in the Deep

Scotland’s Crown Jewels — the Honours of Scotland — are the oldest crown jewels in Britain. The crown, sceptre, and sword of state were created during the reigns of James IV and James V and first used together for the coronation of Mary Queen of Scots in 1543. During times of national crisis, they were hidden deep within the castle. But perhaps the most remarkable hiding place came during World War II: when invasion threatened, the Crown of Scotland was concealed in David’s Tower — buried inside a medieval latrine closet. It’s a detail almost too extraordinary to believe, yet entirely true.

The Stone of Destiny, upon which ancient Scottish kings were crowned, was also kept at the castle for centuries after its return from England in 1996. In 2024 it was moved to its permanent new home at Perth’s City Hall museum — but its connection to Edinburgh Castle remains part of the story of this rock and the nation it helped define.

The Well That Held History — and Small Change

Cut deep into the volcanic rock, the Fore Well was the castle’s primary water source throughout the medieval period. It first appears in historical records in 1314, when Robert the Bruce’s troops deliberately blocked it to deny the English garrison their water supply. In more recent times, laser scanning and archaeological investigation of the well revealed a fascinating mix of eras: a complete cannonball, fragments of others, a brass military button, an 1795 halfpenny — and, at the bottom, a plastic toy skeleton and modern small change dropped by tourists. The deep past and the present, sitting together at the bottom of a very old hole.

The Tunnel, the Fireplace, and the Piper Who Never Came Back

When a new service tunnel was blasted through the rock in the late 1980s to ease vehicle access, engineers cut straight through an underground room. The result is one of the castle’s strangest features: a fireplace, set incongruously into the rock wall mid-tunnel — a small window into an entire buried room that the modern world simply drove through.

There are also believed to be tunnels running beneath the Royal Mile, with at least one said to connect the castle to Holyrood Palace. The government has never confirmed their extent — the castle remains in military use and defence secrets endure. Legend says that a young piper from the Royal Piper Corps was once sent into the tunnels to map their route by playing as he went. The music stopped. He never returned. Searches months later found nothing. A sealed chamber was reportedly discovered years on, containing a skeleton in a piper’s uniform. Some say on quiet nights, the faint sound of bagpipes can still be heard drifting up through the streets of the Old Town.

“Beneath Edinburgh Castle lies not one story, but thousands — stacked in layers of stone, bone, and legend. Every dig reveals another world that had been quietly waiting.”

What Else Is Still Down There?

The honest answer is: we don’t fully know. Parts of the castle have never been fully excavated. Sealed rooms remain. Geological surveys suggest more tunnels exist than have been officially confirmed. The castle is still a working military site, which means full archaeological access is never straightforward.

If you’re visiting Edinburgh Castle, don’t just look up at the ramparts. Think about what’s beneath the ground you’re standing on — centuries of kings, prisoners, secrets, and stories, pressed into the rock of a volcano that erupted before there were people to see it. That’s the real magic of this place.

👉 Curious about more of Edinburgh’s underground world? Explore the Real Mary King’s Close — one of the most haunting hidden streets in Scotland.

👉 Why is the Royal Mile so famous?

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