Mound

A map by Ernest Cooper of the earthworks they found and their understanding of how the sea port would have been laid out.

A satellite image of the mound with a scale

There is a historically significant mound and ditch (52°21′52″N 1°39′38″E / 52.3644°N 1.6605°E / 52.3644; 1.6605 (Frostenden Mound)) typically described as in Frostenden and associated with the sea port recorded at Domesday, but actually across the parish boundary in South Cove.^[16][17] It is approximately equidistant between Frostenden Corner and Cove Bottom.^[17] It is a suspected Viking-era Danish fortification,^[18] the only one in Suffolk identified by Ben Raffield's study of the National Monuments Record, Medieval Archaeology, Archaeology Data Service, and Suffolk's Historical Environmental Record.^{[19]: 6, 29}

The site may have been excavated by Eustace Grubb, which would have predated Morley's involvement.^[16][20]

It was first suggested as a Danish fortification by Claude Morley in 1924, after finding a site on the nearby river bank that he suspected to be the Domesday port.^[18] Ernest Cooper, writing with Morley, stated that the fort was built to protect the port, which included a dock in which the Vikings would lay up ships for the winter,^[18]: 178 though also said it may be a ship burial.^[18]: 179 Sometime between its discovery and 1951, Hugh Braun suggested it was too small to be a Danish fortress and was more likely the location of a Normal hall.^[21]

The site was the excavated by Peter Woodard in January to February 1951.^[16] He told journalists that it might be a ship burial,^[22][23] but later stated in a letter to the East Anglian Daily Times that it was only one of a number of possibilities he was considering.^[24] During the excavation, he found glazed tiles (which he dated to the thirteenth century^[24]), a Gallic pot,^[25] the foundations of a wall, the remains of timber, evidence of burning and a mound of burnt flint at the jetty.^{[26][27][lower-alpha 4]}

Basil Brown visited the site with Guy Maynard (then curator of Ipswich Museum) during the excavation (on 31 January), and suggested it might have been constructed to prevent landing from the river.^[28] Woodard finished the excavation in May 1951, declaring it to be inconclusive and that a large scale excavation in the future by someone more competent than him would be needed to tell.^[29] However, he said "for various reasons" he remained convinced that it was a ship burial.^[29]

It was surveyed again by Charles W. Phillips, working as an archaeological officer for Ordnance Survey in 1954, who stated that it was unlikely to be a ship burial as these were constructed on the highest available land near the water, and the mound is within a slight valley.^[30] He added that while it was not impossible for it to be a fortification, "it is very oddly sited in relation to the surrounding ground", again because of the valley.^[30] Phillips described the suggested dock as "not impossible but very difficult to prove."^[30]

The site was surveyed again on 11 January 1972. The surveyor stated that "its position rules out the possibility of it being a round barrow, motte, or windmill mound" and that the suggested dock "is a line of natural slopes".^[30]

The river was dredged around 1978, during which pottery, oyster shells, and bones were found, possibly from where the docks were situated though the location was not recorded.^[16][20]

Gatehouse Gazetteer opined that statements dismissing the possibility of it being a fortification were probably overstated and "based on false ideas about the function of castles."^[31] It describes it as "a ditched mound, with a palisade and clearly used in C11."^[31]