Hidden Valley Observatory is an astronomical observatory owned and operated by Black Hills Astronomical Society. Located just outside Rapid City, South Dakota (USA), the observatory sits on the edge of the Black Hills National Forest. The grounds include an outdoor classroom and observation field. The public is welcome on specific dates listed on the society's website. See also List of observatories References External links Hidden Valley Observatory Clear Sky Clock Forecasts of observing conditions. Astronomical observatories in South Dakota Buildings and structures in Rapid City, South Dakota Education in Pennington County, South Dakota Tourist attractions in Rapid City, South Dakota 1960s establishments in South Dakota