The lake is long and narrow and lies in an east–west orientation, mostly in Barron Township except for the southeastern end which is in Stratton Township; it is entirely within Algonquin Provincial Park. The primary inflows are the Barron River from its source at Clemow Lake at the west and Carcajou Creek that enters the lake over the Carcajou Falls at the head of Carcajou Bay at the southeast.[2] Primary outflow is the Barron River, controlled by the Grand Lake Dam, which flows at the east to Stratton Lake and further via the Petawawa River to the Ottawa River.
The lake is notable as the location where Tom Thomson painted The Jack Pine.[4] There are also some petroglyphs on the granite cliffs on the north side of Carcajou Bay.[2]
Tributaries
"Right" and "left" are with reference to the Barron River.