Sakhalin is a large Russian Island located at the east coast of Russia and north of the Japanese Island of Hokkaido. It is the main island of the Sakhalin Oblast. It covers an area of 72'492 square kilometres. The highest elevation is the Mount Lopatin (1'609 m) of the Eastern Sakhalin Mountains.
Russia 2002, Three Brothers.
The rock formation is a set of three monolithic rocks jutting out of the water about 3 km west of the town Alexandrovsk-Sakhalinsky on the northwest coast of the island Sakhalin.
(note: there is another rockformation with the same name and an existing postage stamp, located in Avacha Bay on Kamchatka Peninsula)