Andean Architecture

The Power of the Trapezoid

Note the trapezoidal window typical of Inca construction. The trapezoid and lintel appears to replace the arch which they had not discovered.

Window from Machu Picchu

The three window temple shows the trapezoidal windows even more clearly.

The indigenous people of South America developed a different technique of wall building that was well-suited to an earthquake prone area. Rather that repeated rows of bricks or rectangular stones, they interlock the stones in the different levels (courses) of the wall.

This close up shows the interlocking better.

The Inca developed this technique to the highest point. Note that here the large stones have been cut to interlock like a jigsaw puzzle. They were shaped so precisely that no mortar is necessary. This was done with harder rocks. They did not have iron; there are few iron deposits in South America.

After giving an effusive description of the beauty of the sun temple, Hiram Bingham, the modern discoverer of Machu Picchu writes, “The elusive beauty of this chaste undecorated surface seems to me to be due to the fact that it was built under the eye of master mason who knew not the straight edge, the plumb bob or the square. He had a good eye, an artistic eye, an eye for symmetry and beauty of form. His product received none of the harshness of mechanical and mathematical accuracy. The apparently rectangular blocks are not really rectangular. The apparently straight lines of the courses are not actually straight in the exact sense of the term.”

Bingham’s words are true enough. But he doesn’t seem to realize that straight courses of rectangular stones slide and fall in an earthquake. The slightly rounded and accurately `machined’ surfaces of the Inca stones make a much stronger wall.

Here we illustrate this precision with a block with corner cut out.

The Inca learned this technique from earlier peoples. The pyramid in Lima illustrates the entire principle. They built in interlocking trapezoids.

The picture above shows original wall built in interlocking trapezoids. Budt on the right, the wall is built of regular rows of `indentical bricks’. This is a reconstruction and UNESCO requires that the reconstruction be distinguishable from the original. According to the guide at the pyramid site, during an earthquake at another site in Ecuador in 2007?, the reconstruction collapsed and the 700 year old pre-Inca wall still stands.

John Baldwin, Aquas Calientes, May 28, 2008.