One of the oldest cemeteries in Europe has recently been discovered, with graves dating back almost 8,500 years. Two of the most intriguing finds are the skeleton of a six-month-old child and a mysterious upright burial of a man in his early 20s.

The German cemetery, called Gross Fredenwalde after a nearby village, belongs to a time known as the Mesolithic, when Europe was populated by hunter-gatherers. At a press conference Thursday morning in Berlin, excavators announced that nine skeletons have been uncovered on the hilltop burial site so far, five of them children younger than 6 years old. And the researchers found ample evidence that more graves remain unexcavated.

“It’s rare for the Mesolithic to find multiple graves in one place,” says forensic anthropologist Bettina Jungklaus, who excavated one of the bodies. “They were mobile people, ranging over the landscape.”

Excavations in 2013 and 2014 uncovered evidence of the prehistoric graveyard, found 50 miles north of Berlin on a hill 300 feet above the plains below. The hilltop’s hard, rocky soil would have been a tough place to dig graves. With no water sources nearby, it would have been a bad place for a settlement, too.

In a paper published in the journal Quartär, Thomas Terberger, the archaeologist who led the recent dig, says the burials are evidence of careful planning. “It’s not an accumulation of burials by accident, but a place where they decided to put their dead,” says Terberger, of the Lower Saxony Department of Historic Preservation. “It’s the first evidence of a true cemetery in northern Europe or Scandinavia.”

That, colleagues say, makes the spot special. “It’s a big surprise,” says Erik Brinch Petersen, an archaeologist at the University of Copenhagen. “Hunter-gatherer people typically buried their dead right next to their houses. Here in northern Europe, a site like this is unique.”

The infant skeleton is rare, too. Researchers say it’s the earliest infant skeleton ever found in Germany, and one of the oldest in Europe. Excavators removed the fragile remains from the cemetery in a single, 660-pound (300 kilogram) block of earth, making it possible to carefully expose the 8,400-year-old skeleton in the controlled setting of a lab. “It’s really rare to find an intact burial like this, because an infant’s bones are so small and fragile,” says Jungklaus.

Laid to rest not long after it turned six months old, the baby is almost perfectly preserved, its arms folded across its tiny chest. The bones and nearby soil are stained red from ochre pigment used to decorate the body for burial.

The excellent preservation offers researchers a wealth of information. Chemical signatures in the bones, for example, could show whether the infant was breast-fed; DNA could establish links to other skeletons in the cemetery and determine the infant’s gender.

Learning more about its short life and how it died could tell archaeologists more about what conditions were like for Europe’s early inhabitants. “We can look at possible illnesses, and perhaps determine the cause of death,” Jungklaus says. “Children are always the weakest link–they’re the first victims when the environment or living situation changes.”

While the infant burial is remarkable, the body of a young man found nearby has excavators puzzled–and excited. Buried more than 1,000 years after the infant, the man was entombed standing up, together with bone tools and flint knives. The man’s skeleton suggests he lived a pretty easy life. It doesn’t show signs that he did a lot of physically taxing labor. “He looks like a flint knapper or experienced craftsman, rather than the strongest boy of the group,” Terberger says.

Stranger still, the vertical grave was filled in just as far as the man’s knees at first. His upper body was allowed to partially decay and fall apart before the grave was filled in. At some point, a fire was built on top of the tomb.

WATCH: Get a glimpse of the well-preserved, 8,400-year-old skeleton of a baby found in Germany.

One possible explanation comes from hundreds of miles to the northeast. Standing burials similar to the one at Gross Fredenwalde have been found in a cemetery called Olenij Ostrov in modern-day Russia, from about the same time. Researchers have long assumed culture flowed into ancient Europe from the south, but these odd burials suggest that there was active migration or communication across northern Europe as well. “This man is an indication of such eastern influences,” Terberger says; DNA results from his bones might be able to tease out the connections.

From early analyses of his DNA and the grave goods he was buried with, it’s clear the young man buried standing up was a hunter-gatherer, like the infant he shared the cemetery with. But he died about 7,000 years ago, meaning the hilltop cemetery was in use for more than a millennium.

His death occurred about the same time the first farmers arrived in this part of Europe, part of a process that changed the face of the continent. The overlap might help researchers understand what happened when hunter-gatherers first encountered immigrants bringing new technologies and lifestyles from far to the south. “Late hunter-gatherers and early farmers lived side-by-side,” Terberger says.