Lake Santo Parmense is an oligotrophic dimictic lake of glacial-tectonic origin located in the Tuscan-Emilian Apennines National Park at an altitude of 1507 m a.s.l. It is the largest and deepest natural water body in the Northern Apennines, with a surface of 8.2 ha and maximum depth of 22.5 m. The period of ice cover usually lasts from November to May. It was naturally fishless, but underwent regular fish stocking since the beginning of the 20th century. There is a hut (Rifugio CAI Mariotti) on the shore of the lake, including a restaurant, dormitories and meeting room, 220 V power supply (open in summer and on request in other times too). It can also be reached by a chair lift. A small boat is permanently stationed at the lake for sampling operations. Limnological research on the lake started in the 1950s and continued until nowadays, although with several discontinuities. Research topics that have been addressed over the years at the lake include phytoplankton and zooplankton ecology and phenology, predation/competition interactions and energy fluxes through pelagic food web, evolution of trophic state, sensitivity to acidification and climate change.