Lake Cadagno (Italian: Lago di Cadagno) is a meromictic lake in the Piora valley (canton of Ticino) Switzerland. As one of a few meromictic lakes in Europe it is the object of numerous scientific studies. The Piora valley - located in the Gotthard massif (central Swiss Alps) in the Southern part of Switzerland near Airolo at an altitude of 2000 m above sea level - is a landlocked alpine valley whose scientific value has been recognized for more than two centuries. Given a list of categories: company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, what category does the paragraph belong to?
The answer to this question is:
Natural Place