Maybe it's the altitude, but come summer, the Mile High City unleashes a series of kooky happenings ranging from the world's largest Zombie Crawl (a horde of 7,000 blood-splattered zombies) to the world's largest gorilla run (1,200 fully costumed gorillas...and growing). Visitors are welcome to dress appropriately and join the shenanigans. Here's a guide to Denver's crazy, fun-filled summer:
1) Every Wednesday night through Sept. 26, thousands of costumed bicyclists take to the streets for a moving pub crawl known as Denver Cruisers. Bike riders dress according to themes (examples include Space Invaders, Duct Tape & Cardboard, Pirates, Punk, Goth & Glam) and travel from pub to pub through the back streets of Denver neighborhoods, finishing with a scary-looking, but generally safe "Circle of Death," a ride in which huge circles of riders pedal into an increasingly smaller circle.
2) Celebrate the 30th Anniversary of the Colorado Gay Rodeo from July 13 - 15 at the Jefferson County Fairgrounds. This year's event includes traditional rodeo events such as team roping, bull-riding and flag racing, but also incorporate some GLBT twists - wild drag racing, steer decorating and goat dressing.
3) Run for Your Lives in the race of a lifetime at the Thunder Valley Motorcross Park on July 14. This 5K obstacle course pits you – the living – against a horde of zombies who will chase you through a series of obstacles including pools of "blood" and undead infested forests. A dozen bands will play following the race, whether or not there are any survivors.
4) Summon your inner sleuth for this year's Mile High Murder Mystery, a mad dash to gather clues on whodunit throughout Downtown Denver on July 14. Last year, there were 700 costumed characters competing, with prizes going to the top three teams. Music, drinks and food follow the awards ceremony at Stoney's Bar & Grill.
5) Military training may come in handy for Denver's Urban Assault Ride happening throughout the streets of Denver on July 22. Teammates set out on a citywide quest for "checkpoints" on their two-wheeled steeds – with tasks such as tricycle "trike" races, slip-n-slides and dance competitions throughout.
6) Catch blue ribbon fever at this year's Denver County Fair from August 10 to 12, where you can enter more than 30 truly crazy competitions. Find out who has the best Mile High City mustache; who the fastest texter in the west is; who does the greatest chicken impression; who rocks the best Frida Kahlo unibrow; who can build the fiercest fighting robot, and a whole lot more.
7) As John Cougar would say, Denver's Retro Run "Hurts So Good." Dig out your Jane Fonda workout wear and leg warmers for this 1980s-inspired 5K around Sloan's Lake Park on Aug. 26. Prizes will be given to best costumes – including best dressed pet – and break dancers and 80's music will have you "Shakin" like Eddie Money.
8) If you haven't experienced New Belgium's Tour de Fat, you've missed out on bicycling giraffes, superheroes, ballerinas and the most random costumed characters you may ever see on two wheels. Don your craziest costume and head to Denver's City Park for the parade on Sept. 8, and enjoy live music, delicious craft beer and sunshine the rest of the day.
9) Did we mention Denverites love zombies? In 2011, more than 7,000 of the undead lurched along 16th Street Mall, and the horde is expected to grow for another record-breaking year during the Denver Zombie Crawl on Oct. 20.
10) It's hard to count how many Denver residents own gorilla suits, but there are at least 1,200 who donned theirs – with modifications – for the Denver Gorilla Run, happening this year on Oct. 27. Wynkoop Brewing Co.'s event raises funds for the Mountain Gorilla Conservation Fund, and each registrant is provided with a gorilla suit to keep for next year's race.
Click on Visit Denver for more information on the Mile High City.
For more information about top events in Colorado take a look at the Top Events USA selection of the annual main festivals and events in Colorado.