Two trenches are being dug in Ipswich town centre as part of an archaeological investigation.
The work is ahead of a £3m redevelopment of the Cornhill, which will start in January and see the creation of a water feature and sculpture.
The investigation trenches will be in a fenced-off area and the work is expected to take two weeks.
Shops, restaurants and market stalls will be open as normal.
The dig follows similar work in July 2016, when Ipswich Borough Council said nothing of significance was found.
Initial plans drawn up to improve the town square included levelling of the Cornhill and a tower.
Following a public consultation, these were dropped in favour of a more traditional design.
The scheme is being funded by Suffolk County Council, Ipswich Council and the New Anglia local enterprise partnership.
The borough council will lead the project.