Yerkes Observatory

Yerkes Observatory is a restored historic observatory in Williams Bay, Wisconsin, home to the world's largest refracting telescope and active science-and-arts programming. The building is open to the public only for staff-guided tours and scheduled events, with advance reservations required; it is not an unrestricted walk-in museum. The surrounding grounds and trails are generally open from dawn to dusk unless a private event closes them, while tours involve substantial walking and stairs and accessibility varies by space. Check the official tour and event calendar, ticket availability, weather and any private-event closure before travel.