No visitor to Denver should miss out on the chance to see the stupendous 9000 seat Red Rocks Park Amphitheatre, which was carved out of a cliff face during the great depression, and hosts many concerts and shows during the summer months every year. The acoustics are sensational within the amphitheatre and seeing a performance there is a highlight of a visit to the city. If you aren't there during the concert season, then the Red Rocks Park is still open to the public and you can always get a friend to sit in one of the seats while you get on the (gigantic) stage and sing them a song.