Geneva 15.7%. Of the agricultural land, 0.3% is used for growing crops. Of the water in the municipality, 0.2% is composed of lakes and 2.9% is rivers and streams. The altitude of Geneva is , and corresponds to the altitude of the largest of the Pierres du Niton, two large rocks emerging from the lake which date from the last ice age. This rock was chosen by General Guillaume Henri Dufour as the reference point for surveying in Switzerland. The second main river of Geneva is the Arve, which flows into the Rhône just west of the city centre. Mont Blanc
Conservatory and Botanical Garden of the City of Geneva with the posthumous donation of the de Candolle herbarium. In its present location, it occupies an area of adjacent to Lake Geneva and the park of the United Nations Office at Geneva and ranks as one of the five most important in the world. The gardens themselves were designed by . The Botanical Garden's greenhouses initially remained at the Bastions site for financial reasons. Then, in 1910–1911, the architect Henri Juvet built a Winter Garden along the former Chemin de Varembe, which was moved to its present location close to the railway lines following the construction of the Palais des