Catalyzes the conversion of D-fructose 1,6-bisphosphate to D-fructose 6-phosphate. In vitro, has also weak activity with inositol-1-phosphate, glucose-1-phosphate and glycerol-2-phosphate. beta-D-fructose 1,6-bisphosphate + H2O = beta-D-fructose 6-phosphate + phosphate Inhibited by Li(+), ADP, ATP and glucose-6-phosphate. Optimum temperature is approximately 100 degrees Celsius. Homodimer. Belongs to the inositol monophosphatase superfamily. FBPase class 4 family.