Heck - where to start? Pretty much any creek bed is going to have tons of big boulders to leap around/on/over.
Right near you in Golden, obviously Clear Creek Canyon has lots of opportunities. Bear Creek Canyon (Morrison to Evergreen) below Lair 'o The Bear park where the road goes through a series of s-turn - there are some great opportunities down in the channel. Clear Creek Park in Golden and west of the park......ooh....here's a good one: right where the paragliders land there is a water canal that comes off Clear Creek somewhere above Tunnel 1. Follow that canal up and there are places where one side is a big wall, where there are boulders next to it and farther up there is this crazy lattice work of wood to protect it (I guess) from falling boulders.
Pretty much every ski area has cliff and boulder areas that would be great for Parkour in the summer.
Boulder - heck, the place is called Boulder - pretty much everywhere. Every switchback on Flagstaff plus the summit. Gregory Canyon, anywhere along Boulder Creek from Foothills Parkway to Ned. Settler's Park, Gregory Canyon - up behind the old hospital on Mapleton.
Coal Creek Canyon just east of Pinecliff. There are some good spots in Golden Gate Canyon state park - hang a right (north) at the visitor's center and start looking for rocks. Just about any place above Timberline. Underneath Gray's and Torrey's Peak. Take the Bakerville exit, drive up the dirt road until you have a chance to turn right. Park and head down to the creek. Like I said, pretty much any creek bed will have tons of good Parkour terrain.
I can go on and on. I grew up above Boulder and used to do stuff that now seems very Parkour. I had a revelation last week. I'm going to just paste in something that I posted to Parkour.net. I hope Colorado people find it inspirational:
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I grew up in the mountains above Boulder, Colorado. Since I was a kid - don't know when it really started, it just evolved - we would play on rocks, run trails, etc. As I got older - in my teenage years - I came to formalize it a bit. We called it just "trail running" and some times (slightly different) "screeging". We took our inspiration from skiing and it was just something to do in the summer. We'd run down trails, bouncing from side to side on the rocks, catch some air, do a little "grab" or something. Play around dropping off of large rocks, jumping across gaps in rocks, across gullies, etc. Screeging would be an imitation of skiing down very steep slopes with an emphasis on large drops from boulders. We also did a lot of rock climbing, mountaineering, etc. and jumping off cliffs into lakes and small pools in mountain streams. It translated into an urban environment sometimes when we'd be down in town and see something and be like "oh, that's sorta like a mountain" and play around a bit.
I first became aware of Parkour about a year ago when a friend sent me a Russian Parkour video. I thought it was extremely cool and have spent time searching for other videos while bored at work and have watched quite a few. Never really thought much about it beyond it being cool to watch. Never thought it related to me, never thought it was something I could do.
Then for whatever reason, I was watching a video and it suddenly hit me how similar the discipline is to what I've been doing in the mountains for years. I spent some time yesterday and today reading about the philosophy and the underlying intent and have realized that what I was doing wasn't just similar to Parkour - it IS Parkour! It was all about moving fluidly through the environment and overcoming obstacles - both for fun and out of necessity. How do I get across that stream to get to my friend's house without going a mile downstream to the bridge? Well - if i leap off that rock, grab a branch, swing over and bounce off a mid-stream boulder and dive for the far bank, I'm there!
An example of a routine run I used to do that now seems very Parkour:
When I was in my early 20's I was doing Enduro motorcycle racing semi-professionally. Part of my training was to wake up every morning and run up the mountain behind my house. I dunno - maybe 1000 vertical feet. At the top was a redrock "hogback" and I'd climb that and chill out for awhile taking in the view. Coming down would be the fun part. "Dance" down the rocks like on skis, then leap for a convenient tree branch and swing over the rubble at the base of the rocks and onto grassy ground. From there it would be a short flat trail run that would gradually transition to cutting across a steep slope. Leaving the trail, run/"ski" down the steep slope, leaping off some rock here and there. Get setup to cross a water canal cutting across the slope. That would be a precision leap from the high side of the canal onto the little trail that ran along the low side of the canal.
From there, run along the canal a short distance to a game trail that dropped down. The initial entrance to this would be a big drop into a "belly" of loose, soft sandy soil. The trick here would be to gain traction to follow the trail to the right rather than spilling out awkwardly down the slope. The trail would kind of peter out into a gully that led to a big willow tree, but if you stayed high you could do a Saut de Bras across the gully grabbing a root on the little ridge on the far side. From atop this little ridge, it was possible to transfer onto a big, fat horizontal limb of the willow tree. Near the trunk there were all sorts of possibilities but the fast way down would be to just jump off onto the big, loose soft face of the gully. Any trick was possible as the landing was very safe.
From there out from under the willow on a little trail then leaving the trail down towards my house. This was pretty brushy and would involve sneaking under branches and leaping over branches and fallen logs. Down to the creek behind my house, the only way to stay (sometimes) dry was to do another Saut de Bras to a high spot on the far bank with a desperate lunge for a root at the top. Scramble up the bank, then a little leap to my upper deck then a big leap across a big gap to my lower deck - home!
Anyway, thank you for indulging me in that long story. As I'm sure you can tell, I'm suddenly very excited about Parkour and it has brought back a flood of great memories. I hadn't thought about that routine in years. I could bore you to death with all my Parkour-like adventures (I once used similar techniques while escaping from a sudden storm down a snow-filled couloir on a 14k foot peak). I'm getting a bit old now but do still emply the techniques when I'm in the mountains and plan on experimenting with urban Parkour during my breaks from my office job in the city.
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Anyway, I live pretty close to you, Demon, on Green Mountain. I have to get my old butt in shape, but I could definitely show you some of what I'm talking about sometime.
Chris