Fillmore Auditorium The Fillmore Auditorium is an auditorium located on Colfax Avenue and Clarkson Street in Denver, Colorado, United States. Founded in 1999, it is used for performances of live music. It is named after The Fillmore, a famous establishment in San Francisco. The building opened in 1907 as a skating rink, serving several different functions over the decades following. In 1969, it was bought by Stuart Green, with the intent of "emulating Bill Graham’s Fillmore". Under the name Mammoth Gardens, the venue hosted such powerful names as The Who and The Grateful Dead, but it was closed in October 1970. By the 1990s, it was operating as the Mammoth Events Center, hosting a mix of public and private functions. Finally, under new ownership, it was renovated and reopened as The Fillmore Auditorium in 1999.