Colorado has so many craft breweries, there are probably some local beers you haven't tried yet. Wynkoop, Great Divide, and Breckenridge breweries all offer free tours.
There are several different art walks around town that feature galleries and street art every first Friday of the month. The biggest one is on Santa Fe, but there's also Tennyson, RiNo, Belmar, and the Navajo Street Art District in LoHi.
This contemporary art gallery houses giant inflatable bunnies and frequently features free tours and workshops, often with free refreshments, too.
4. Get a mile high
No, not like that. The 13th step on the Capitol's stairs is the exact marker of 5280ft, or one mile above sea level.
There are free movies playing throughout the summer at Skyline Park, Infinity Park in Glendale, and Civic Center.
6. Skate the Denver skatepark
Show off your skills at one of the 25 best skateparks in America. Or if you have no skills, there are always plenty of skaters and bikers to watch.