Colchester Castle in Essex is an example of a Norman castle, and is a Grade I listed building, in which you can still see many of the original Roman materials used in its construction (such as Roman clay). The Castles keep stands at 46m x 34m, and is not only the largest keep ever built in Britain, but is also the largest surviving keep in Europe.
The Castle itself was built roughly around 1080, on the foundations of the Roman Temple of Claudius (built 55AD). The remainders of the foundations and their massive vaults can be viewed today on the Castle tour. The construction of the Castle was ordered by William I, who demanded a royal fortress be built in Colchester.
Believe it or not, from as far back as 1226, the castle was used as a prison, most famously by Matthew Hopkins in 1645, who imprisoned, interrogated and tortured suspected 'witches' within its walls. Prison cells built in 1727, complete with intimidating oak doors and barred windows, can be seen today on the Castle tour.
The award-winning castle museum was opened to the public in 1860, and is now home to displays such as the 1648 Siege of Colchester, collections of ancient gold coins and even its own Egyptian Mummy! Visitors can tour the Castle rooves, Roman Vaults and the Norman chapel, before enjoying a lovely picnic in the Castles adjoining park. However, the Castle is currently undergoing a huge re-development and will be closed to the public until spring 2014.