Lancaster's most imposing building is the castle, built in 1150 but added to over the centuries: the Well Tower dates from 1325 and is also known as the Witches' Tower because its basement dungeon was used to imprison the accused in the infamous Pendle Witches Trial of 1612. Also dating from the early 14th century is the impressive twin-towered gatehouse. Visits are by guided tour only as the castle is used as a Crown Court.
Also imprisoned here was George Fox (1624–91), founder of the Quaker movement. The castle was heavily restored in the 18th and 19th centuries to suit a new function as a prison, and it continued to house Category C prisoners until 2011 – the A wing of the prison is part of the guided tour.