A westwork, forepart, avant-corps or avancorpo is the monumental, west-facing entrance section of a Carolingian, Ottonian, or Romanesque church. The exterior consists of multiple stories between two towers. The interior includes an entrance vestibule, a chapel, and a series of galleries overlooking the nave. A westwork is usually broader than the width of the nave and aisles. It is sometimes used synonymously with narthex. The structural purpose of the massive westwork is to resolve the horizontal thrust of the east-to-west arcades of the nave. Church towers as a part of a church began with the construction of the first westworks.