A short walk from the cathedral, this 900-year-old fortress was once one of the most powerful strongholds in medieval England. Lincoln Castle dates from the time of William the Conqueror in 1068. Nothing remains of his original fortress. On one of the mounds where the original castle stood is the Lucy Tower, dating from the late 12th century. The East Gate also dates from the 12th century. The castle came under siege in the wars of 1135 to 1154 and again in 1216 to 1217. During the 19th century, it functioned as a prison. You can see the prison chapel with its self-locking cubicles; these cages kept prisoners from seeing each other. Inside its exhibition rooms is displayed one of only four surviving copies of the Magna Carta. Much of the appeal of a visit here involves walking along the top of the wall that surrounds the fortress, overlooking the castle's grassy courtyard, the city of Lincoln, and its cathedral.