This trail caught my attention on the REI hiking project site . With Rocky Mountain National Park, National Forest, Larimer open space, Boulder open space, preserves and State parks - It is a challenge to know what one can do where (and when) and this website seems to have the best information.
I first spied this collection of rocks from Rocky Mountain national park in the summer. From a distance it looks like a big version of the Pinnacles, pretty similar from close up too.
The lake is frozen solid. Not knowing how thick the ice was we stayed at the shallow end, but I'm pretty sure at was at least 6 inches thick.