Please answer the following question: Pick one category for the following text. The options are - company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work. Montfichet's Tower -  Montfichet's Tower (Mountfitchet's or Mountfiquit's Tower or Castle) was a Norman fortress on Ludgate Hill in London between where St Paul's Cathedral and City Thameslink railway station now stand. First documented in the 1130s it was probably built in the late 11th century. The defences were strengthened during the revolt of 1173–1174 against Henry II. It was demolished in 1213 by King John and the site sold in 1275 to build the great Dominican priory of Blackfriars.
A:
Building