This is the main gate to the entire religious compound of Shāla, quite close to the city of Rabat, Morocco. The portal is flanked by two towers, or bastions, one on each side. These towers are seemingly identical to one another. The towers were clearly constructed with red-orange bricks, as is the rest of the structure; though, the brick-work/bricklaying is not nearly as visible in the walls or around the portal. Constructing the towers from brick is a logical move because the medium works well with the shape of the structure. The towers were designed semi-octagonally, making them structurally sound and simple to build with a uniform material. Because all of the bricks are the same size, it is easy to make all walls of the tower proportional.
There are intricate, yet low relief designs surrounding the portal and some parts of the towers. The patterns on the towers are confined to the highest section, which rises above the walls of the gate. The sculpture around the main portal is in the highest relief. The design works with the shape of the horseshoe arch as archivolts do around the circular part of a tympanum. The innermost “archivolt” has a scalloped pattern which starts and ends with the horseshoe shape of the arch—though the structure of it extends down the sides to the ground, the pattern does not. The “archivolt” outside of that is designed with similar scalloping, but the individual shapes of the scallops are designed to almost be trefoiled, whereas the inner scallops are rounded. Where the horseshoe arch is pointed, at its highest point in the center, the “archivolts” are pointed as well. Above the outermost point, there is a simple relief of a diamond shape.
Though they are farther up, and therefore more difficult to see from the ground, the relief sculpture on the towers is more elaborate. The top of the tower extends to a square shape, rather than a semi-octagon. This extension creates triangular shapes in which the artists were able to create a honeycomb like texture/pattern called muqarnas. At the base of these triangles, there are three smaller, arch like designs. Within the relief of the oddly shaped arches, are intricate geometric patterns. These shapes are mimicked in lower relief carvings on adjacent sides of the tower, along with some inscriptions.
Kamal Lakhdar "Challa Necropolis" in Discover Islamic Art, Museum With No Frontiers, 2018. 2018. http://www.discoverislamicart.org/database_item.php?id=monument;ISL;ma;Mon01;5;en
Nagy, Péter Tamás. “Sultans' Paradise: The Royal Necropolis of ShÄLa, Rabat.” Al-Masāq, vol. 26, no. 2, 2014, pp. 132–146. Taylor and Francis Online, doi:10.1080/09503110.2014.915103.