The Tinmal Mosque is one of the most important historical monuments in Morocco and one of the best-preserved examples of Almohad architecture anywhere. Built in 1153 to commemorate Ibn Tumart — the religious reformer who founded the Almohad movement in this very valley — the mosque served as the spiritual and political heart of an empire that would go on to control North Africa and al-Andalus. The dynasty's first great architect, Abd al-Mumin, designed it on the same principles he would later apply to the Koutoubia in Marrakesh.
What you see today is a roofless but largely intact shell: massive pisé walls enclosing a forest of horseshoe arches, the minaret still standing, the mihrab (prayer niche) decorated with intricate carved stucco that has survived eight centuries of exposure to mountain weather. The interior is open to the sky, which gives the arches and the light a drama that no intact mosque interior can quite match. Non-Muslims are freely permitted to enter, making it one of a very small number of historical mosques in Morocco accessible to all visitors. A caretaker is usually on site; a small tip is expected and entirely appropriate.