I found an article on the internet from 2007 about the oldest (known) solar observatory in the Americas.  This is a site known as the thirteen towers which was discovered over a hundred years ago but only recently recognized for what it is.  The towers mark the rising and setting arcs of the sun over the course of the year.  This group of structures is believed to be about 2300 years old and is near the ruins of the ancient Chankillo temple.   
    I find it fascinating that ancient people beginning about ten thousand years ago started building structures that charted primarily the movement of the sun.  One theory on this is that about eleven thousand years ago a major catastrophe that effected the entire planet changed the orbit and caused the poles to be tilted out of alignment had left the ancients with a new sky to chart.  The tilted axis caused drastic changes and it became important for people to chart those changes so they could be prepared for them, at least, those that changed on a regular basis such as the four seasons.