The Allegheny Observatory, an operating research observatory of the University of Pittsburgh, sits inside Riverview Park on Pittsburgh's North Side (about four miles north of downtown), at 159 Riverview Avenue. A private research laboratory that is not always open to the public, it welcomes visitors through free guided programs by reservation: evening public tours (Fridays April–October and Thursdays May–August, 8–10 p.m.), monthly public lectures, and day or evening group and school visits. A tour includes a short presentation followed by a walking tour of the historic building, ending at the 13-inch Fitz-Clark refractor for viewing on clear nights. The observatory describes the building as only partially handicapped accessible, so visitors with access needs are encouraged to contact it beforehand.