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
Geneva Lake with the nearby town of Geneva, Illinois, the city was renamed "Lake Geneva"; later the lake was renamed "Geneva Lake". Lakeshore attractions include Big Foot Beach State Park, Lake Geneva Yacht Club, the George Williams College campus of Aurora University, and Yerkes Observatory. The observatory is owned by the University of Chicago, which has established a study group to plan a regional center for science education at the observatory. Public access to the lake is allowed as the result of a decision by early European settlers that "20 feet of land leading up to the shoreline should be public domain."