Update (Thursday, 11:37 a.m.): The answer is the Montana state capitol building, in Helena, Montana.
DENVER, Colo.--Over the years--and even several times during Road Trip 2009--I've seen a number of these kinds of buildings. They've been, variously, large, banal, awe-inspiring and, in some cases, worth detouring to see.
This one is different than the rest, however. It just looks unique.
Can you tell me what and where it is? If you're the first to do so (by e-mail, to daniel--dot--terdiman--at--cnet--dot--com) you'll win a prize in the Road Trip picture of the day challenge.
There are only two challenges left after today, so your chances at winning a prize are dwindling. Until Road Trip 2010, that is.