The empire left an extensive architectural legacy, being one of the major medieval Somali powers engaged in castle and fortress building. Many of the ruined fortifications dotting the landscapes of southern Somalia today are attributed to the Ajuran Empire's engineers, including a number of the pillar tomb fields, necropolises and ruined cities built in that era. During the Ajuran period, many regions and people in the southern part of the Horn of Africa converted to Islam because of the theocratic nature of the government. The royal family, the House of Garen, expanded its territories and established its hegemonic rule through a skillful combination of warfare, trade linkages and alliances.