Roman pottery, evidence of a Roman settlement and "possibly Saxon" artefacts have been found at a proposed solar farm site near Peterborough.
The land at Newborough is being excavated ahead of a city council decision about the solar farm plan.
Richard O'Neill, from Wessex Archaeology, described the finds as "locally and regionally significant".
Work is expected to continue for three weeks, after which the council will consider the archaeologists' report.
Plans for the solar energy farm at three council-owned sites at Newborough, Morris Fen and America Farm were put on hold after English Heritage stepped in suggesting the area could be "nationally important".