The Musée d'Histoire des Sciences occupies the Villa Bartholoni, a neoclassical mansion on the lakeside in the Parc de la Perle du Lac, just east of the Palais des Nations. The museum is free, small, and worth more time than most visitors give it: its collection of scientific instruments from the 17th and 18th centuries is one of the best in Europe, including telescopes, astrolabes, globes, electrical machines, and the instruments used by Geneva's own scientists in the period when Geneva was a serious centre of natural philosophy.
The villa itself is handsome, the park is pleasant, and the lake is immediately outside. The combination of a free, uncrowded museum in a beautiful setting within a walk of the UN makes this one of the most rewarding and overlooked afternoons in Geneva. The park's café operates seasonally.