Excavation work at Sheffield's Castlegate is underway with experts hoping to unearth unknown facts about the city's past.
City leaders, councillors and staff from chosen contractor Wessex Archaeology gathered at the site on Monday as the dig officially started.
Archaeologists hope to fund out how much remains of the former medieval castle as well as inviting schoolchildren onto the site to see the work, once they return after the summer holidays.
Milica Rajic, project manager, said it was a 'fantastic opportunity' for the company and that work was due to get underway in mid August.
She said: "This is fantastic from an archaeological point of view. It's every archaeologist's dream to try and find a castle so from that point of view it's extremely exciting.
"It's really nice to dig in Sheffield too because we've got an office in the city so it's just a fantastic opportunity for us."
Ms Rajic said there would be a team of around nine staff initially working on the dig and that they hoped to open up the site so that the public and schoolchildren can see the work being carried out around a week or two into the project.
She said: "We want to make it accessible for all. We want to show what we are thinking is there and hopefully we will find something exciting."
The work will be the first-ever comprehensive investigation of the whole site since the castle was demolished at the end of a Civil War siege, made possible by the demolition of Castle Market in 2016.
Previous archaeological work was confined to either observation by dedicated amateurs when construction was taking place and two trenches on the market’s upper loading bay back in 2002, which were excavated by the University of Sheffield’s commercial team.
The archaeology team will host tours for schools, community and heritage groups and the public, working with the Castlegate Partnership which includes the council, the Friends of Sheffield Castle, the University of Sheffield and Sheffield Hallam University, and businesses.
Joy Bullivant, of heritage group Timewalk, who has written a report on the history of the site and the regeneration potential of the area, said: "What I understand, and I am no great expert, is when they knocked the castle down sometimes they just filled the space in with the rubble and levelled the site a bit so there could be all more than we realised.
"There could even be remains of the wooden castle which was there before they built the stone one."