TGIF

I moved here from Charlotte, N.C., where they put historic plaques on buildings that predate World War II. Here in Massachusetts, our oldest buildings date to the 17th Century. Now comes word from Peru that archaeologists have unearthed what may be the oldest known structure in the hemisphere -- built about 5,500 years ago.

That's about a thousand years before the earliest of the Egyptian pyramids.

The plaza (pictured) was found at Sechin Bajo, 230 miles north of Lima. It is less than 40 feet across, built of rocks and adobe (bricks of dried mud). Archaeologists believe it was used for ceremonial purposes.

It sits in a region where scientists previously have found evidence of one of the world's oldest human settlements, roughly contemporary with settlements in Mesopotamia, Egypt, China, India and central America. But the oldest of the previously discovered ruins was a citadel built about 5,000 years ago.