Built on the foundations of the Roman Temple of Claudius, Colchester Castle is the largest Norman keep in Europe.

Now a museum, it showcases the history of Colchester from Celtic kings, through the Roman invasion and Boudiccan revolt, to the Norman conquest and medieval life.

But there is plenty which goes on behind the scenes which you may not know about - and the Gazette has been given access to a few of these areas.

In one part of the castle lays a hidden vault...and the jury is out on what is was originally intended for.

A spokesman for the museum said: “Perhaps for storage, or maybe it is an oubliette, from the French ‘to forget’.

“An oubliette would have been a gruesome end for any person placed in it.”

An oubliette or secret dungeon was a room with access only via a trapdoor at its ceiling.

The spokesman added: “A time capsule was placed in the hidden vault in July 2014 by Colchester Young Archaeologists, with the thought of it being opened in 2039.

“It contains local and national newspapers, a comic, an e-cigarette, a light bulb, and a blackberry smartphone with pictures of Colchester and the YAC members and a message for the future.

“There is a picture of the Queen and the Duke of Edinburgh, sent from Buckingham Palace, McDonalds’ toys, loom bangles and friendship bracelets, a YAC badge and photographs of YAC members outside Roman Circus House.”

Other items include coins, Odeon cinema listings and CDs and DVDs and some One Direction merchandise.

Among the unusual items in the castle is a Roman roof tile with a paw print in it.

The spokesman added: “The paw print on the Roman tile was made by a dog walking across it almost 2,000 years ago, when it was still soft, presumably before being fired in a kiln.

“The tile is in the Roman vaults. If you take the Castle Tour, you can ask the guide to show you it.”

Women accused of witchcraft, people imprisoned for their faith and those desperate enough to steal bread for their family all spent time in the castle prison.

And they leave their mark even today, with graffiti covering the walls.

The spokesman added: “The scratches by the prison cell bars were likely made by an inmate desperate for release.

“There are many examples of graffiti to be seen if you look carefully – horses, a sailing craft and initials amongst them. A cell could hold up to 40 prisoners, often kept in the dark.”