Because of the high inside humidity of the stone chamber of Takamatsuzuka Tumulus and the high water content of the lime plaster walls, fungi appeared on the walls inside the chamber. In order to develop protective measures against this problem, the moisture regime and thermal regime of the tumulus were studied by installing apparati to measure water content profiles and temperature profiles of the mound surrounding the stone chamber. Sampling of the mound soil and sounding tests were also carried out to clarify the present condition of the mound. Based on these studies, it was decided to cool the stone chamber to reduce biological activities by installing cooling pipes in the mound surrounding the stone chamber
