Researchers said divers working off the coast of the Bjorko island near Stockholm found jetties significantly longer than initially believed, which could provide valuable clues about Viking culture and habits, TheLocal.se reported Tuesday.
Marine archaeologists said they now estimate the village was 30 percent bigger than previously believed.
A marketplace may have been based in the waters of the harbor, they said.
"We have found stone piers in deep water and these were rare for this age," research leader Andreas Olsson said. "Timber, logs and poles as well.
"Previously, it was not thought that the Vikings could build stone piers at a depth of eight meters (26 feet)."
The jetties, five times longer than previously believed, show evidence of the Vikings' extensive trade system, Olsson said.
"The remains of the port structures show that it was actually a port, not just small jetties jutting out onto the beach as previously thought," he said.
The discovery was made near the village of Birka, which is generally considered Sweden's oldest settlement and has been a U.N. Educational, Scientific and Cultural Organization World Heritage Site since 1993.