While the Incas never invented either a written language or the wheel, their society was still a highly advanced and technical society with developed culture and traditions. Although Incan sculpture and pottery did have a unique style which influenced much of the art created in pre-Columbian South America, the crowing achievement of Incan aesthetics was their incredible ability to build, without the aid of metal tools or mortar, buildings and structures made of stone blocks which fit together so closely that after hundreds of years once still could not insert a knife blade between them.
The photographs and the notes on the photographs above are taken from the book, The Ancient Art of Peru by Heinrich Ubbelohde-Doering. The number at the top of the text corresponds to the page on which the photograph appears in Doering's book.
From Josh Marcy's, Topher Wilkins' and Adam Tarnoff's ID1 paper.