Researchers of the ELSA laboratory in collaboration with Bianca Jackson of Michigan University, USA visualized the internal structure of a Russian icon of the 19^th century. The icon was sounded by terahertz radiation in two regimes: reflecting and transparent. In the first case, pulses reflected from the interface between lacquer, paint, ground and the wooden base were recorded. This permitted reconstructing the layer structure of the icon, in particular, finding the difference between thicknesses of the lacquer, paint and ground at different points on the icon surface. Pulses that had passed through the icon were recorded in the transparent mode, allowing determining the density of matter average over icon thickness at different spots. The results obtained permitted the researchers to answer the restorers’ question about the cause of refreshing the image on a small section of the icon. The terahertz scans clearly featured the defect of the internal structure of the wooden base in the form of a knot (there were no traces of the defect on the back side of the icon). This enabled the researchers to reject the hypothesis about a candle burn of the icon and to choose a right restoration procedure.