The City Wall
Scholars have stated that the city wall in a dream symbolizes its ruler or governor, and an unknown wall might refer to Islam, knowledge, wealth, and security. If one sees the city wall destroyed, it could indicate the death or removal of its ruler. As for one who sees themselves building a wall, it often signifies fortification and protection from enemies or tribulations, or benefiting from knowledge or marriage that provides security.
Per Ibn Sirin's Muntakhab al-Kalam fi Tafsir al-Ahlam