If you've been to Fes, Morocco, you'll immediately recognize the Grande Porte Bab Boujeloud, also known as "The Blue Gate of Fes." If you exit through the Bab Boujloud, however, you'll note that its other side is actually green.

The towering entryway with its mosaic tiles is the most iconic portal to the old medina, Fes el-Bali, the world's largest surviving medieval city and urban car-free zone. The blue on the side that greets new visitors represents the color of the city of Fes, which is famous for its pottery, painted with elegant cobalt blue designs. The reverse side, which faces the medina, is green—the color of Islam.

Built in 1913, the bab (gate) is a doorway between two equally colorful and dynamic scenes, one that feels distinctly 21st century, and the other an intriguing mix of different eras.

Once you pass through "The Blue Gate," the thrum of traffic will quickly fade, replaced by the din of shopkeepers selling their wares and the muffled footsteps of thousands of animals and pedestrians making their way through the winding alleyways. From the Bab Boujeloud entrance, you'll come upon the two main alleyways into the medina, the Tala'a Kbira and Tala'a Sghira—though whichever you take, you'll probably get lost.

There are several eateries just inside the gate, and if you find a table on an upper perch, you can watch the mesmerizing and never-ending movement of people and wares from above, passing to and fro.