Machu Picchu, one of the seven wonders

Machu Picchu, a city built by the Incas only 500 years ago still standing in almost perfect condition. The rocks are all perfectly square and so close together, you can't get anything between them.

With their primitive tools, they were able to cut tongue and grooves on all of the rocks, which is why they are still standing today with no mortar, or any substance, holding them together. I guess the tongue and groove patent really belongs to the Incas.

There was also a lot of really neat sculptures that look like bizarre rock formations, but are representative of their idols of worship during the summer solstice. For example, a strange bunch of rocks projects the shadow
of a panther on a certain day annually. Imagine doing all of that work, for one hour per year of reward!