The river Bille is a small slow-flowing river in Stormarn Schleswig-Holstein a right tributary of the Elbe. Its source is near Linau north of the Hahnheide forest. It then flows south of Trittau representing the border between Stormarn and Lauenburg continues south of Reinbek and reaches the river Elbe near Billwerder. A lot of old estates and tasteful parks are laid out along its riverbank. 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?
A:
Natural Place