Travel to the southwestern-most vigilantes in the poor district of Damascus. 
On one of the buildings around them, you should see an outcropping in the wall, 
climb on it and you will see that it looks exactly like G1 Optimus Prime in 
vehicle mode. Note that there may be more than one outcropping in the area, 
so look carefully. If you lose sight of the vigilantes, you have gone too far.