However, the most significant find may well be the brick-barrel drainage network built in the 19th century.
It will also continue to be used into the future.
Central city plan project director Dr Glen Hazelton told an audience in Dunedin yesterday evening the stormwater system was built well and much of it could be rehabilitated and reused.
He was one of the presenters at a Southern Heritage Trust event at the Dunedin City Library.
The multimillion-dollar George St upgrade was largely driven by the need to replace old water pipes and sewers, but the vast majority of the stormwater system in the central business district was in quite good condition, Dr Hazelton said.
He showed a video taken within the stormwater network featuring space up to 1.5m tall.
He described the overall project as complicated.
Some elements of historical underground infrastructure did not exist on maps, he said.
New Zealand Heritage Properties principal archaeologist India Gillespie said artefacts ranged from an old decanter to more commonplace items.
"People, surprisingly, lost a lot of shoes in Dunedin back in the day."
Other items uncovered included historical roading, crossings that made it easier to traverse the "muddy gauntlet of Dunedin", driveways, kerb and channelling.
People grew unhappy about the state of Dunedin in the 1850s.
This led to the establishment of basic infrastructure in the following decades and upgrades, Ms Gillespie said.
