Geophysical investigation of hidden wall passages in the historical building of Hungarian Academy of Sciences

The main building of the Hungarian Academy of Sciences is a neo-Renaissance palace built in 1865 in Budapest, situated on the eastern bank of the Danube River. In October 2018 MinGeo Ltd. was entrusted with the task of the inspection of hidden wall passages and chimneys connected to the ceremonial hall of the Academy in order to improve its ventilation. For this purpose, we used ultra-high resolution GPR inside the building; endoscope camera and cable locator in the chimneys. With this method five wall passages were found on the ground floor of the ceremonial hall and seven on its gallery, while we had an indication of a passage at 8 locations in the Museum hall on the floor above. The GPR measurements also revealed 4 so far unknown passages in the southern wall of the ceremonial hall. With the opening of the outlet of these four passages the ventilation of the hall could easily be improved. If this is not enough, there are several more passages connected to the chimneys, which also could be utilized for this purpose.