Arc - The construction element.
It has been known of for more than 1000 years. The whole point in it is its structure. An arc is suported by the two walls or pillars and the weight which lays upon it is given to its supporters.
Arc was used for the first time as we know (as we have records) in Persia around 3rd century. Many other nations copied it. In Roman style during 11-13 century arc had a great servise in churches.
This is one way of constructing arc.