Additional Website: Facebook. "Avogadro's Number has been a cultural staple of Fort Collins for over 40 years. Known to our loyal patrons simply as "Avo's", this historic music venue and restaurant has captured and held the hearts of generations of Coloradoans. Avo's is a unique double-venue, with both an intimate indoor venue, and an expansive outdoor venue. The oudoor venue is open May through October, and boasts water features, a treehouse, a large gazebo, and concessions so that patrons can enjoy beer and barbecue without missing a note." Shows are held Thursday-Sunday nights with open mic on Tuesdays and a Bluegrass Jam on Wednesdays, but other nights are possible.