The upgrades are more than a year in the making, but for a 16,000-year-old archaeological site, that's nothing.

Meadowcroft Rockshelter, near Avella, is reopening to the public Saturday after undergoing a massive renovation that will make it an accessible tourist destination for people who want to see what is considered the oldest archaeological site in North America.

Compared to neighboring Meadowcroft Village -- a slice of rural life in 19th century Western Pennsylvania that drew about 12,000 visitors last year -- the Rockshelter had fewer visitors, despite its impressive historical significance.

The site was discovered in 1955 when Albert Miller found some archaeological evidence in a groundhog hole on his property. A few of the artifacts were linked to ancient hunters, and in 1973 archaeologist James Adovasio, then at the University of Pittsburgh and now at Mercyhurst College, asked to excavate.

When Dr. Adovasio sent some artifacts to the Smithsonian for radiocarbon dating, the findings suggested humans had lived there as early as 16,000 years ago -- 4,000 years earlier than remains in New Mexico that were thought to be from the first North American inhabitants. The data were disputed at first, but after numerous tests and debates, the archaeology community has accepted the notion of humans living in Washington County in 14,000 B.C.

In the decades since, the site has struggled to attract tourists because the old facility had a poor view of the crucial area, where excavations continue, and could only accommodate a few spectators.

But Meadowcroft Director David Scofield said the improvements that will be revealed this week -- in addition to better protecting the area under a permanent roof -- will help draw big groups and make the Rockshelter a well-trafficked tourist stop. It also doesn't hurt that the U.S. Department of the Interior designated the site a national historic landmark in 2005.

"As soon as we get the word out [about the improvements], we expect visitors from all over the U.S. and around the world," Mr. Scofield said.

The new structure, which incorporates the rock face in the ceiling, will offer grand views of Cross Creek, about 50 feet below the rock shelter.

"Basically the new shelter approximates where the old overhang existed, however many tens of thousands of years ago," said architect Rob Pfaffmann. "It interprets what it must have been like to camp at that site."

It also will allow large groups to have a good look at the excavation site, with more material to tell visitors the story of the Rockshelter. In addition, Meadowcroft will have an "interpreter" on site to answer questions and guide groups and individuals through.

Helping to connect the Rockshelter to the more popular Village will be a 17th century Native American village, parts of which will open this summer, showing how North Americans lived before Europeans arrived.

It's all part of a $4 million upgrade to Meadowcroft, including $1.3 million for the Rockshelter project, raised from state grants, foundation money and private donations.

The centerpiece is the new enclosure, built at a 17-degree angle and anchored to the rock face.

"For an architect, this is a once in a lifetime project," Mr. Pfaffmann said. "You don't get to do one of these every day."