With a 1375-acre surface area, Carmi is the fourth largest natural lake entirely within Vermont. It is 7.5 miles around, averaging about 20 feet in depth, and is 33 feet at its deepest point.  The lake supports northern pike, walleyes, and other warm water species. The lake drains north into Quebec’s Pike River, then into Lake Champlain. Lake Carmi was once much larger. In the thousands of years since the last ice age, the southern end of the original lake has silted in, creating wetland forests and the third largest peat bog in Vermont.

Most of the 140-acre bog lies within Lake Carmi State Park and is a designated State Natural Area. Natural Areas have been set aside for the preservation and protection of their unique ecological, geological, or scenic and contemplative values. The road to Camping Area “B” cuts through the bog and is the northern boundary of the Natural Area. The high ground on which Camping Area “B” is built would be an island if not for the bog.

The Lake Carmi Bog is characterized by spindly black spruce trees, with lesser  numbers of  tamarack trees. Shrubs, especially mountain holly, form a thick and nearly impenetrable understory. The ground plants includes pitcher plants, sedges, sphagnum mosses and other typical bog plants. This black spruce-tamarack bog is largely undisturbed and is unusual in Vermont for its size.

The state park includes over two miles of frontage on the south and east shore of Lake Carmi. Most of the 482-acres were purchased in 1959. The park was developed in stages through the 1960’s. Some of the land is under agricultural license so the open fields are maintained by farming activity.

There are 140 tent/trailer sites, 35 lean-to sites, and 2 cabins that make this the state's largest campground. Rest rooms have running water and hot showers($). There is a trailer dump station but no hookups. Most sites are large enough to accommodate self-contained RVs. There are swimming beaches in both camp areas. There is also a day use beach with a nature center, rest rooms and rental boats.