Archaeologists have found two rare boat burials from the Viking age in Sweden, offering what they say is a glimpse into how customs and practices changed in the tumultuous era of raids, religious conversion and trade.

The burials were found in Gamla Uppsala, underneath a plot of modern houses near a parish, said a Swedish research firm, called the Archaeologists, that is part of the state-run National Historical Museums.

The researchers have yet to confirm the age of the graves, but believe they date to the 10th century. One of the burials had been damaged, likely when a cellar was built nearby, but the other was found intact, with the remains of a man in the stern of the boat.

A horse and a dog were buried in the bow of the boat, with a sword, spear, shield and ornate comb. The buried man was likely a very wealthy member of Viking-age society, said Johan Anund, the regional manager for the Archaeologists.