The city's Grand Mosque has ancient heritage. It's built on a rise above the inner port where early Berber and Phoenician inhabitants built a place of prayer. The Romans later turned this into a temple which was then converted into a Christian basilica. This was later torn down and replaced, in the 11th century, by the mosque, which has since been much altered and enlarged.
Inside the five doors the prayer hall is supported by rows of columns, 72 in all, and contains a cedarwood minbar, which carries an inscription stating that the mihrab, the niche indicating the direction of Mecca, was constructed in 490 AH (AD 1097). This supports the idea that the mosque was built by Youssef ben Tachfine, the Almoravid ruler of Tlemcen, at a time when the Mediterranean was transformed by the First Crusade.
The minaret, 15m high, carries an inscription urging us to contemplate its beauty and the magnificent appearance of its crowns.
It is normally open to non-Muslims outside of prayer time, but consider taking a local guide with you.