The Lacawac Sanctuary includes some 530 acres (1300 ha) of second-growth oak and hemlock forest and forested peatland surrounding Lake Lacawac, a 53-acre (21 ha) natural lake. The Sanctuary property extends south beyond the watershed of Lake Lacawac over steep sandstone ledges down to the shore of Lake Wallenpaupack, a 5,600-acre impoundment that today is a major recreational area and economic focus of the local economy. Two small ponds constructed in the early 1950's occupy a small spring-fed tributary to Lake Wallenpaupack.

Lake Lacawac is a nearly pristine natural lake that has been largely spared the human agricultural and residential development that has altered the appearance and biological communities of most lakes in the region. This mesotrophic, slightly humic-stained lake occupies a basin excavated by the late-Wisconsinan glacier into nearly flat-lying beds of sandstone and shale of the Devonian Catskill Formation. The 15,000 year-old lake is fed by seepage from its small watershed of peatland and forested uplands. Having a maximum depth of 43 feet (13 meters), Lake Lacawac is biologically rich, with well developed planktonic, littoral, and benthic communities. Beaver, muskrat, and otter use the lake, as well as at least nine species of fish. White-tailed deer, porcupines, turkeys, skunks, and black bear are often encountered. Plant communities of special interest and value for preservation include the Lake Lacawac littoral zone, the forested bog of the north and western lakeshore, and the Wallenpaupack ledges.

In recognition of its exceptional value as an example of a rapidly disappearing habitat within the Pennsylvania and New Jersey region, in 1968 Lake Lacawac was designated as a Registered National Natural Landmark by the National Park Service. Swimming and fishing are not allowed in the lake - except for pre-approved scientific purposes - in order to protect this habitat. Rowboats and canoes are available to explore the picturesque lakeshore.