Bab Mansur al-'Alj

[6] Its name comes from the architect and designer of the gate, Mansour al-'Alj (the "Victorious Apostate"), a former Christian slave who converted to Islam.

[8]: 391 In the early 19th century, Sultan Moulay Abd ar-Rahman added a loggia-type structure just outside the gate on the right (southwest side), which is no longer present today.

[13][12] Inside, the gate's passage is bent, turning 90 degrees twice,[7] and bridges the distance between the double walls of the Kasbah, granting access to Place Lalla Aouda beyond.

This consists of a repeating darj-wa-ktaf motif (stylized lozenge-like pattern in Moroccan architecture) which frames the main archway of the gate and fills the spaces above the columns of the flanking bastions.

The empty or negative spaces within this motif are entirely filled with colourful polychrome zellij (mosaic tilework),[6][7] another feature which was new to Moroccan monumental gateways.