Given the 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. Fort of Greta (Horta) - The Fort of Greta (also referred to as the Castelo da Greta Forte da Guia or Forte da Nossa Senhora da Guia da Horta respectively: Castle of Greta Fort of Greta or Fort of Our Lady of the Guide) is a medieval fortification whose remnants are located on the cinder cone of Monte da Guia along the southern coast of the civil parish of Angustias in Horta island of Faial in the Portuguese Azores.
The answer is:
Building