Both Bierstadt and Evans offer high altitude running possibilities. As do Grays and Torreys. A fun and thoroughly adventurous long run at altitude, given stable conditions, is to trot from Loveland Pass to Guanella Pass. All you'll need is a car at either end... and the ability to run 14+ miles (and climb 7200 feet) at between 12,000 and 14,200 feet...
