In May 2006, archeologists announced they had found a pre-colonial astronomical observatory, possibly 500 to 2,000 years old, near Calçoene. The age is based on pottery sherds on site that have been dated to 2,000 years old. The site is on a hill and has 127 large stones blocks of granite, each 3 meters (10 ft) high, and dug firmly into the ground. Archaeologist Mariana Petry Cabral of the Amapa Institute of Scientific and Technological Research (IEPA) said that the observatory has been designed to align with the winter solstice. Other agricultural societies also developed sophisticated ways to track important times in the solar calendar. At one time, researchers did not think any cultures in the Amazon Basin had developed such complexity as to build such a site. This has altered their thinking.