The Main Door was designed during the first third of the 13th century as the majestic entrance to the church, exuberantly and richly decorated in geometric, plant and animal motifs.  However, some significant parts are missing for example the upper cornice which used to crown this door and all the corbels which once held it up. These mutilations are the result of the cathedral's transformation into military barracks in the mid-18th century when the cloister was divided up into compartments over two floors to house infantry troops.

Although it may be hard to tell, you are looking at what used to be, at one time, the cathedral's main façade.

Notice the Main Door is not alone. Two others join it: the door of the Evangelist on the left and the door of the Epistle on the right. These three doors, which lead to the church’s three naves, comprise the lower body of the façade, while the upper body is presided over by a rose window, which can only be seen from inside the temple.

Both the façade and the Main Door lost their functions when, in the late 13th century, when construction was practically finished, it became necessary to add the cloister which, as you’ll have seen for yourself, is constructed, atypically, as a continuation. The explanation is quite simple: there wasn’t enough space at the sides of the church. This curious and unique fact made it necessary to build a new façade and, thus, a new entrance, which –located across from where you are now– is known as the Apostles door.