Abstract <p>The aim of the article is to study the specific features of geophysical fields and parameters in the area of a man-made underground water tunnel. Self-potential signals (SP) were measured using nonpolarizing electrodes and and ERA-MAX electrical exploration receiver (SPE ERA, St. Petersburg). The magnetic exploration studies were carried out with MMP-203 proton magnetometer (Geological Exploration plant, Leningrad). Electrotomography was carried out using Skala-48 multielectrode electrical survey equipment (LLC KB Electrometry, Novosibirsk) with the Schlumberger symmetrical survey scheme. The microseismic background was recorded using an OMAR-2s autonomous seismic station (IGF UB RAS, Yekaterinburg). The georadar survey was carried out using SIR-3000 ground penetrating radar and antennas with frequencies 100 and 270 MHz (GSSI, USA). Graphs of magnetic and self-potential fields, electrotomographic and microseismic sections, and a radarogram are presented, which are based on the results of surveys on the research profile. The studies show different levels of the magnetic field and SP in the area of volcanic rocks and gabbro–dolerite dikes. A significant increase in microseismic noise with an increase in weathering crust thickness was observed. Above the underground water tunnel, a local decrease in SP, an anomaly of increased values of electrical resistance values, and intense reflections of radio waves from the top of the tunnel were recorded. The geophysical signs of the boundaries between geological structures and man-made underground objects are revealed. The exact position and depth of the old underground water tunnel have been determined.</p>