1066, the date of the Battle of Hastings, is one date every schoolboy knows.
William the Conquerer sought to rapidly consolidate his victory by building a chain of castles across England.
Lincoln Castle was one of the first castles the Normans built, constructed in 1068, only two years after the defeat of Harold at Hastings.
The castle occupied what was the site of a former Roman fortress. According to the Domesday Book, 166 Saxon homes were cleared to make way for the castle.
Until the construction of Lincoln Cathedral, the castle dominated the Lincoln skyline.
Lincoln was one of the most important cities in the country. It had a mint. The size of the Norman castle reflects its importance.
The view from the castle is still impressive, even today. In one direction, out along the River Witham, Bardney and beyond. In the other direction can be seen the power stations in the Trent Valley.
The castle walls are still intact, and it is possible to walk around most of the wall.
The castle is unusual in that it has two mottes. It is only one of two such castles in the country, the other being at Lewes in Sussex.
The Observatory Tower is built in one of the mottes. The original tower was built 1150 towards the end of The Anarchy (the war between Stephen and his cousin Matilda for control of the throne). Later additions were added in the 14th century. The tower, as we see it today, was added by the prison governor John Merryweather, nominally as a observation post to catch escapees, but in reality, as he was a keen astronomer, for star gazing. During World War II it was used as a fire-watch post.
The other motte is the Lucy Tower. Built in the 12th century by the Castle Constable, the Countess Lucy, this was the castle's main keep, built to replace an existing building. Originally it was surrounded by a 20-foot ditch with a bridge leading to the steps. It was the castle's last line of defence. Within the tower are the graves of prisoners executed at Lincoln.
One of the prisoners whose graves can be found within the Lucy Tower is that of William Frederick Harry, hanged 1 April 1872 for the murder of his wife. His grave is marked with his initials.
The main entrance to the castle is the East Gate from Castle Square. The West Gate has been recently re-opened. The West Gate was important in Medieval times as it led out into open country.
Opposite the newly opened gate is the The Lawn. The main feature of The Lawn is the Sir Joseph Banks Tropical Conservatory.
For 900 years, Lincoln Castle has been used as a castle, a prison and as a court. The Crown Court still sits within the castle. Embedded within the castle walls are the castle dungeons.
Housed within Lincoln Castle is a copy of the original Magna Carta. It is currently on loan from Lincoln Cathedral, and has its own dedicated exhibition.
There are only four surviving copies of the original Magna Carta: two in the British Museum, and one each held by Salisbury Cathedral and Lincoln Cathedral.
Dating from the Middle Ages, The Magna Carta is the most important document conferring democracy and civil rights. It is embedded in English Common Law and has been quoted and drawn on throughout the ages, from the US Constitution (especially the Bill of Rights) through to the UN Charter.
The Medieval Castle Well is believed to be of Roman origin.
The strategic importance of Lincoln Castle cannot be overstated. It had commanding views over the surrounding countryside, it was located on two Roman roads, The Fosse Way and Ermine Street. It also overlooked Brayford Pool, and a waterway that ran from the coast at Boston via the Roman Canal to the Trent.
The castle as we see it today, was the inner bailey. The outer bailey encompassed the then existing town.
The Castle is increasingly being used for concerts and theatrical productions. Several years ago, the Irish/Celtic band Clannad, gave a concert in Lincoln Castle, their only UK appearance that year.
Plans for a multi-million pound revamp and restoration of Lincoln Castle, to be funded by the Heritage Fund, have been put in jeopardy by the billions of pounds being squandered on the unwanted 2012 London Olympics. [Plans for £9.4M revamp to boost tourism and Olympics could ruin Lincoln Castle plans]