Complex sentence: In May 2006, archeologists announced they had found a pre-colonial astronomical observatory possibly 500 to 2,000 years old near Calçoene, which is in the Amazon River basin near French Guiana.
Split into simpler sentences: In May 2006, archeologists announced they had found a pre-colonial astronomical observatory, possibly 500 to 2,000 years old, near Calçoene. This is in the Amazon River basin near French Guiana.