Source: Tafsir al-Ahlam al-Kabir (Ibn Sirin)
The citadel in a dream represents Islam and fortification by it against enemies. Entering it indicates marrying a fortified virgin woman. It is security from fear.
Source: Ta'tir al-Anam fi Ta'bir al-Manam (Al-Nabulsi)
The citadel represents an invincible man, a scholar, or a father. For the traveler, it is a return to his homeland; for the fearful, security; and for the poor, wealth.
Source: Al-Isharat fi Ilm al-Ibarat (Ibn Shahin)
The citadel is interpreted as the king or a fortified man. Entering it indicates security, high status, and marriage. Its demolition indicates the loss of position or the death of a great man.