Mt. Zirkel is the highest point in Routt County and to get to the top of the peak, it is a multi-day hike. I made it up to the saddle in roughly 3.5 hours, but time got the best of me and I had to turn around before making it to the peak. The hike is a roundtrip of 17.2 miles, from the standard route. I've always wanted to do this hike and stay overnight at the Slavonia Mine (the mine is now abandoned, but it does still have a few remnants in the area), which is what most do when they try for the summit attempt. The mine is also a great place to stop and eat some lunch.
The hike to the mines is challenging (but doable if you leave early), gaining several thousand feet (it evens out once you reach the red dirt trail. I did this hike in late July, but luckily most of the snow had melted off and the two river crossings were not too bad (just bring some watershoes)!
I'd also recommend coming prepared for any type of weather, as the you don't have much service out in the Zirkel Wilderness and it can change in a matter of minutes.
Overall, the trail is very well marked (however, don't expect to see many people once you leave Gilpin Lake), but still remember to always bring a compass and map. This hike is great once you get your hiking legs underneath you and the snow has melted (think August or early September).