Archaeologists at the University of Edinburgh are hoping to uncover the scene of a historical unsolved crime.
Work has begun to unearth remnants of buildings which became infamous for the murder of the second husband of Mary Queen of Scots, Lord Darnley.
The remains of the buildings have been buried beneath Old College for more than 200 years.
The dig is being carried out prior to a £1m landscaping project which is being funded by a private donor.
The house where Darnley had been lodging was associated with the Collegiate Church of St Mary, commonly known as the Kirk O' Fields.
It was destroyed by an explosion on 9 February 1567 and although Darnley and his valet escaped, both men were later apparently strangled in the garden.
Mary's third husband, the Earl of Bothwell, was thought to be culpable but was acquitted of the murders two months later.
Remains of mansion
With work under way, archaeologists have made key finds associated with the Kirk O' Fields site, including several burials.
Other discoveries include the remains of Hamilton House, a mansion built in 1552 for the Duke of Chatelherault, and the remnants of the first university library, dating back to 1617.
The excavation is being directed by Tom Addyman of Addyman Archaeology, a division of Simpson & Brown, the university's architects for the landscaping of the quadrangle, in consultation with the City of Edinburgh Council.
University of Edinburgh Vice-Principal Mary Bownes said: "We knew when we began this excavation that there would be lots to discover, hidden beneath the ground.
"What is being revealed is far more than we hoped for, with extensive parts of Hamilton House and other historic sites emerging from the clay and mud."
Councillor Deidre Brock, culture and leisure convenor for the City of Edinburgh Council, said: "This excavation - which could unearth the very building at Kirk O' Fields where Lord Darnley, met his grisly end - offers a tantalising hint of just how much of Edinburgh's fascinating past still lies buried beneath the city."