The castle was expanded several times to house the growing number of Knights. Soon, it became the largest fortified Gothic building in Europe,[6] on a nearly 21-hectare (52-acre) site. The castle has several subdivisions and numerous layers of defensive walls. It consists of three separate castles - the High, Middle and Lower Castles, separated by multiple dry moats and towers. The castle once housed approximately 3,000 "brothers in arms". The outermost castle walls enclose 21 ha (52 acres), four times the enclosed area of Windsor Castle