Think landing a reservation at Casa Bonita is difficult? Try snagging one for a weekday tour of the University of Denver’s Chamberlin Observatory. “They’re sold out for a year in advance, which shocks us,” says Ken Sturrock, a volunteer guide with the Denver Astronomical Society (DAS).

The Romanesque sandstone building’s giant refracting telescope saw the stars for the first time 130 years ago this month, and Chamberlin hasn’t changed much since. Nearly everything in the structure is original, including the hand cranks that deftly maneuver the 26-foot-long telescope, which has charted stars, discovered comets, and almost confirmed Albert Einstein’s theory of relativity during June 1918’s total solar eclipse. (Another observatory got the honor due to unfortunate cloud coverage over the Mile High City.) But the instrument has actually been obsolete for most of its existence and has primarily been used as a science popularizer. In addition to public tours (every Tuesday and Thursday; $4 for adults, $3 for children), DAS also hosts an open house once a month, no reservation required, and the observatory remains an effective teaching tool for the university. “We still have classes here,” says DU physics and astronomy professor and observatory director Jennifer Hoffman, “because it is a really powerful way for our students to envision their place in the universe.”