It is well-known that when the first Spanish conquerors came to the American mainland and first encountered the advanced Indian cultures of Mexico, Central America, and the Andean Plateau, they found remarkable paved roads, passages over and tunnels through the mountains, causeways over lakes, and long suspension bridges.

Everything necessary for a highly developed transportation system except the logical means of transportation – wagons, carts, chariots.  But there were no wheels; everything was transported by safari-like human caravans, or, in the Andes, on the backs of llamas, as well as human beings.

(Charles Berlitz, Mysteries From Forgotten Worlds, p. 53)