"The Tumangan Project", about which much has been written for the last fifteen years has its little known history. The first attempt to create an enclave with a special internationally legal status in the valley of a border river was made one hundred years ago, in 1907-1909. Three parties took part in it - China, Korea, Japan; the latter was the initiator of the transaction. The lower part of the Tumangan river and the adjoining territories have always been, to put it figuratively, a "geopolitical counterpoint". In the VIII-X centuries there was one of the centres of the state of Bokhay, a port connecting it with Japan, in the Expedition bay situated on the Russian side. At the beginning of the XX century the Japanese expansionists called the Chinese territory adjoining the Tumangan river "the back entrance to the mainland".