Bartholomew's Cobble is a 329-acre (1.33 km²) National Natural Landmark, open space preserve, agricultural preserve, and bio-reserve located in southwest Massachusetts in the village of Ashley Falls abutting Canaan, Connecticut. The preserve contains over 800 plant species, including North America's greatest diversity of ferns and the greatest overall biodiversity in Berkshire County, Massachusetts; it also contains Massachusetts' highest populations of ground nesting bobolinks.