Some girlfriends and I went to this rustic spa in the mountains outside of Boulder on Sunday. We didn't stay overnight, so I can't say how the cabins are, but we hiked, had massages, ate an amazing dinner and then went in one of the lakeside spas (shown on their homepage), drank champage, and stargazed. It was awesome. The facilities are a tad outdated, but their prices are very reasonable so we thought the trade-off was just fine.
We're definitely planning a return trip and will stay longer next time.
www.goldlake.com