not knowing why you're going to Denver (business, vacation, family visit), I'd suggest renting a car (reserve in advance to get the lowest prices). Great spots I cannot give you, but you might want to check out the Denver RTD stations Pepsi Center, Alameda Station (UP trackage across the RTD tracks), or just down the street: Broadway Station.
You can also try Globeville Rd. near the La Quinta Inn. There's a yard right next to the river there. This one isn't far from the Union Station.
West 48th Ave. crosses a yard on an overpass just northwest of where I-70 & I-25 intersect, looks like a good place to do some fanning. The last one can be reached by bus from Union Station in about 20 minutes.
Anyway, let me know if you found a good spot. I'd like to check it out myself the next time I'm in Denver.
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