This structure is an example of what are commonly called 'corn dryers', though their actual function is disputed.
This example was excavated at Leadenham, and is now partly reconstructed in the archaeological gallery at The Collection in Lincoln.
Corn dryers are essentially underground flues built, in this instance, from stone.
The flue is 'H' shaped and has a single stoke hole. On top of this would have been a timber building.
The heat from the fire would have warmed the floor of the building above, leading to the suggestion that they were used for drying corn.
More recent experiments, however, have led to alternative suggestions, such as that they were used as part of the beer making process.
Courtesy of Lincolnshire County Council, The Collection