This is a picture of the remains of the wall in Toulouse.  In this picture we can see one of the buttresses.  

Institut Catholique.  Toulouse, France. 

Walls

     Walls were created differently depending on the period, ruler and area of the empire.  Walls were usually created several feet below the ground and were several feet thick.  Metal clamps were sometimes attached between bricks making it difficult to break down.  Again this depends on a number of factors including wall importance, function and time available to create. 

In this picture of the base of the Roman wall in Toulouse, we can see the miscellaneous rubble, such as the apparent column decoration, that was used to create the wall hastily. 

Institut Catholique.  Toulouse, France.