Lake Hovsgol (or Khuvsgul) a.k.a. the blue pearl of Mongolia is located in the northern part of the country. To get there from Ulaanbaatar (UB), you can either fly from UB to Moron or take a public bus (minimum of 18 hours depending on road conditions). Once in Moron, it is easy to catch the post-market transport (15,000T/$10) to Hatgal, at the southern tip of the Lake. The market in Moron is closed on Mondays- so there is no public shuttle until the following day.
There are a growing number of tourist camps in Hatgal so you have plenty of choices of places to stay. Several camps were recommended to us but Garage 24 won us over. It is a converted eco-friendly, communist-era garage which now houses a wonderful hostel. You can choose to stay in either a ger or a 4-bed dorm room. The cost (at the time of posting) is 15,000T for either a ger or dorm bed and all have wood stoves. The food is excellent (we loved the shepard's pie and veggie buuz!) and access to great views and the lake is just a 5 minute walk.
If you're there during high-season, be sure to catch the Sukhbaatar- a tourist boat that takes you around the lake. It was also 15,000T and runs at 12:00 and 15:00- and up to 5 times a day depending on demand.
The area is stunning with options for hiking, fishing, kayaking or just star-gazing. Not to be missed! More info and pictures of this area can be found at: http://globaltravelbugs.blogspot.com/2013/09/northern-mongolia-paradise-found.html