SAO PAULO, Brazil (AP) -- A grouping of granite blocks along a grassy Amazon hilltop may be the vestiges of a centuries-old astronomical observatory -- a find archaeologists say indicates early rain forest inhabitants were more sophisticated than previously believed.

The 127 blocks, some as high as 9 feet, are spaced at regular intervals around the hill, like a crown 100 feet in diameter.

On the shortest day of the year -- December 21 -- the shadow of one of the blocks disappears when the sun is directly above it...

...Cabral has been studying the site, near the village of Calcoene, just north of the equator in Amapa state in far northern Brazil, since last year.

She believes it was once inhabited by the ancestors of the Palikur Indians, and while the blocks have not yet been submitted to carbon dating, she says pottery shards near the site indicate they are pre-Columbian and maybe older -- as much as 2,000 years old.

Last month, archaeologists working on a hillside north of Lima, Peru, announced the discovery of the oldest astronomical observatory in the Western Hemisphere -- giant stone carvings, apparently 4,200 years old, that align with sunrise and sunset on December 21...