from Mount Sivand, where they were quarried in a place called Na'l Shekan ("horseshoe breaker"), to Naqsh-e Rustam to build the Ka'ba. These blocks were chiselled into large, mostly rectangular pieces and are put in place atop each other without using mortar; in some places, such as the rooftop, the stones are connected to each other by dovetail joints. The size of the stones varies from to ; however in the west wall, there is a flat stone that is long. Four large rectangular pieces of stone form the ceiling/roof, placed along an east–west axis. Each of those stones are long, connected to each other by dovetail joints, and the chipping method used to form them has given the roof the shape of a short pyramid. The anathyrosis style is used here in placing the stones atop each other, but no accurate order is retained in the 'ranking' of the stones. In some places, 20 rows, and in others 22 rows of stones are placed, and this continues to the ceiling. Wherever the original builders discovered any flaw in the main stone, the flawed area was removed and filled in with delicate joints, some of which still remain. To prevent the finished building from becoming too simple or monochrome, its creators added two architectural diversities: firstly, forming double-edged shelves from one or two flat plates of grey-black stone and placing them on the walls; secondly, carving small rectangular pits into the upper and middle sections of the outer walls that give a more delicate appearance to the tower's faces. The black stones were probably brought from Mount Mehr in Persepolis, and installed on the walls in three rows: High on the walls just below the ceiling, a small rectangular shelf in the northern side, and two similar shelves on each of the other sides below the ceiling, two large square shelves on three sides and one small rectangular shelf on the northern side below the ceiling, two medium-sized rectangular shelves on three sides and one large rectangular on the northern side Stairway A thirty-stair stairway (each stair is long, wide and high) is placed in the middle of the northern wall, reaching the threshold of the entrance doorway. Thus, the intention was for the Ka'ba to look like a three-floor tower that has seven doors or hatches on each floor; but only one hatch has been made into a true