An ancient granite bridge, called the Frontenac Arch, runs from the northern Canadian Shield in Algonquin Park to the Adirondack Mountains in the United States.

The topography of the biosphere reserve is rugged, consisting of steep, rocky slopes and ridges, typical of the Precambrian Shield.

These alternate with moist forest or wetland valleys inland, and rocky promontories in the Saint Lawrence River known as the Thousand Islands.

Characteristic species of the area include the pitch pine (Pinus rigada), the black rat snake (Pantherophis spiloides) – Canada’s largest reptile and a threatened species, the least bittern (Ixobrychus exilis) – the smallest member of the heron family and listed as a species of special concern, the great blue heron (Ardea Herodias), the osprey (Pandion haliaetus), the common loon (Gavia immer), the bald eagle (Haliaeetus leucocephalus) and the pine warbler (Dendroica pinus).

Water-oriented recreation and tourism are major economic sectors in shoreline communities along the Saint Lawrence River, the Rideau Canal and Charleston Lake.