Construction of the Baikal-Amur Mainline; the track layer is working. Transbaikalia: taiga, mountain ranges Kodar and Udokan. Udokan copper deposit in the Charskaya valley. Search parties of the Udokan geological expedition. Geologists are examining rock samples. There is a drilling rig for soil research. Copper ore sample. Hydrologists are examining the water of the river, hot spring, glacial water. The hydroelectric plant is in operation; ground water is supplied. Geologists who discovered the underground sea; girl geologist dancing under a stream of water.