The unearthing of an underground tunnel has delayed construction at Bannerman Park in St. John's, as city and construction crews try to figure out what to make of the discovery.

Construction workers made the discovery this spring, and speculation about the use for the tunnel has covered all bases — from old sewer lines to a potential escape tunnel for politicians.

Once the tunnel was found, the City of St. John's called in archaeologist Roy Skanes, who works with the architecture company Stantec, to do some further digging.

Skanes said when crews found the stonework of the tunnel, which was obviously old, the city contacted the Department of Tourism and the provincial archaeology office got involved.

Colonial Building construction Bannerman Park

A multi-million dollar restoration of Colonial Building and its surrounding grounds has resulted in the unearthing of a nearby tunnel or drain. Workers have yet to discover if it connects directly to the building itself. (CBC)

He said the tunnel is roughly 37-metres long, two feet wide and just over three feet tall.

"There have been other pieces of stonework unearthed in that area and they turned out to be drains for water drainage because that area of Bannerman Park was at one time a swamp or a bog. This one was quite large to be a drain, so the other possibility of course is that it was a tunnel, which hasn't been confirmed in any way, but certainly it was quite large," said Skanes.

According to Skanes, a wooden base in the space has piqued interest in a lot of people and raised some questions about how effective it would have been as a drainage system, furthering rumours of an alternate use.

"It's really hard to prove. We've got other little lines of inquiry we'd like to look into, one of which was looking at photographs from when they excavated the north wall of the Colonial Building. If it was a tunnel or drain, certainly they would have gone through that stone wall," said Skanes.

"There's several rumours that it was a tunnel used by Richard Squires to escape from the Colonial Building during the riots. Information we have, we certainly can't confirm that. All we can really say is that it seems to be a very large drain compared to the other ones that were found there."

Likely an old water drain

However, local St. John's archaeologist Gerry Penney said it's unlikely there's any real mystery to the structure.

Bannerman Park construction workers

A steady stream of construction on Bannerman Park and the Colonial Building started last year in an effort to revitalize the downtown park. (CBC)

Penney said he thinks it's an older stone-lined drainage system, similar to ones found in other older areas of the city.

"It's a water and sewer tunnel and deliveries and such things, but I haven't seen any tunnels that are pedestrian — that lead from one place to another," he said.

"Even though there are rumours of tunnels underneath the harbour and tunnels between Colonial Building and Government House and tunnels other places, I haven't seen them."

While the mystery may be debunked, workers are still hoping to find out if the tunnel connects to Colonial Building and where it leads.